Engine component layout for outboard motor

An intermediate drive mechanism allows an alternator to be mounted beneath an engine flywheel on the side of the engine. This location reduces both the girth and height of the engine, thereby reducing the size of the power head of an outboard motor. The intermediate drive mechanism includes a first intermediate pulley, which lies generally at the same level as a drive pulley attached to the engine output shaft. A second intermediate pulley lies beneath the first intermediate pulley and generally at the same level as a driven pulley of the generator. Belts couple the pulleys of the intermediate drive mechanism to the respective drive and driven pulleys. The intermediate pulleys also can move relative to the corresponding pulleys so as to function as a belt tensioner.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates in general to an internal combustion engine. 
In particular, the present invention relates to a layout of engine 
components of an outboard motor. 
2. Description of Related Art 
In a conventional arrangement of an alternator in a V-6 marine engine, the 
alternator lies near the valley formed between the cylinder banks of the 
engine. A crankshaft of the engine drives the alternator by a pulley 
system. 
The pulley system commonly involves a crankshaft pulley attached to an 
upper end of the crankshaft and an alternator pulley attached to a rotor 
shaft of the alternator. A belt couples together the pulleys to transfer 
power from the crankshaft to the alternator. 
The conventional position of the alternator in the valley between the 
V-shaped cylinder banks of the engine results in the engine having a large 
size in the fore to aft direction. The protective cowling which surrounds 
the engine thus must has a sufficiently large size to account for this 
extended engine length. 
The large distance between the crankshaft pulley and the alternator pulley 
also requires that the belt have a wide width to prevent the belt from 
warping or twisting. The required large width of the belt, however, causes 
the height of the cowling to extend well above the upper end of the engine 
block, resulting in a large cowling. Because the power head of a 
conventional outboard motor commonly extends well above the transom of the 
watercraft, a larger sized cowling produces more drag on the watercraft. A 
larger and thus heavier cowling also contributes to a greater overall 
weight of the watercraft which the outboard motor must propel through the 
water. Both of these effects affect the performance of the outboard motor. 
SUMMARY OF THE INVENTION 
A need therefore exists for an improved engine layout for the electrical 
generator within the engine which reduces the length and height of the 
outboard motor's power head. 
One aspect of the present invention thus involves an engine that comprises 
a vertically-oriented output shaft which rotates a drive pulley. The drive 
pulley is attached to the output shaft at an upper end of the engine. A 
generator is mounted at a side of the engine and includes a driven pulley. 
The driven pulley is positioned at a level below the drive pulley. An 
intermediate pulley system operates between the drive pulley and the 
driven pulley to transmit power from the output shaft to the generator. 
In accordance with another aspect of the present invention, an engine 
includes a vertically-oriented output shaft journalled within a housing. 
An upper end of the output shaft extends above an upper end of said 
housing. A generator is positioned to a side of said engine at a level 
below the upper end of the output shaft. Means are provided for 
transferring power from the output shaft to the generator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1, there is illustrated a conventional alternator arrangement in a 
V-type engine 1, the basic understanding of which is important for an 
appreciation of the present invention. FIG. 1 illustrates a prior engine 
layout used with a V-shaped cylinder block assembly 2. A crankshaft 3 of 
the engine 1 carries a conventional magneto-flywheel 4 at its upper end. A 
pinion gear 5 of a starter motor 6 cooperates with a ring gear 7 of the 
flywheel 5 in a conventional manner. The starter motor 6 lies on one side 
of the engine 1. 
An alternator 8 is positioned to lie generally within a valley formed 
between the V-shaped cylinder banks of the cylinder block assembly 2. The 
crankshaft 3 of the engine 1 drives the alternator 8 by a pulley system. 
A crankshaft pulley 9 of the system is attached to an upper end of the 
crankshaft 3 above the flywheel 4. An alternator pulley 10 is attached to 
a rotor shaft of the alternator 8. A belt 11 couples together the pulleys 
9, 10 to transfer power from the crankshaft 3 to the alternator 8. 
The conventional position of the alternator 8 in the valley between the 
V-shaped cylinder banks of the engine 1 results in the engine 1 having a 
large size in the fore to aft direction. In addition, because the belt 11 
is tightened by moving the alternator 8 in the aft direction, the 
protective cowling which surrounds the engine 1 must leave room for such 
adjustment. This further increases the size of the outboard motor power 
head in the fore and aft direction. 
As best seen in FIG. 2, the large distance between the crankshaft pulley 9 
and the alternator pulley 10 also requires a wide belt 11 to prevent the 
belt 11 from warping or twisting. The required width of the belt 11 causes 
the height of the cowling to extend well above the upper end of the engine 
block 2, resulting in an increased size of the engine 1, as noted above. 
FIG. 3 illustrates an marine engine 12 which is configured in accordance 
with a preferred embodiment of the present invention. The present engine 
layout reduces the size of the engine 12 and therefore has particular 
utility for use in an outboard motor 14 because of the space confinement 
within a protective cowling 15 which surrounds the engine 12; however, the 
depiction of the invention in conjunction with an outboard motor 14 is 
merely exemplary. Those skilled in the art will readily appreciate that 
the present engine design can be applied to marine engine used with 
inboard/outboard drives, with personal watercraft and in other types of 
watercraft engines as well. 
As understood from FIG. 3, the engine 12 is mounted conventionally with its 
output shaft 16 (e.g., crankshaft) rotating about a generally vertical 
axis V. The crankshaft 16 drives a drive shaft (not shown) which depends 
from the power head 18 of the outboard motor and extends through and is 
journaled within a drive shaft housing 20 (FIG. 4). The drive shaft 
depends into the lower unit 22 to drive a propulsion device 24, such as, 
for example, a propeller or a hydrodynamic jet. 
The engine 12 desirably is a reciprocating multi-cylinder engine operating 
on a two-cycle crankcase compression principle. In the illustrated 
embodiment, the engine 12 has a V-type configuration, and specifically a 
V-6 cylinder arrangement. The present invention, however, may be 
applicable to engines having other cylinder arrangements, such as, for 
example, in-line or slant cylinder arrangements. 
A cylinder block assembly 26 lies generally at the center of the engine 12. 
The cylinder block includes a pair of inclined cylinder banks 28. The 
cylinder banks 28 extend at an angle relative to each other to give the 
engine a conventional V-type configuration. As understood from FIG. 3, a 
vertical central plane A lies between the cylinder banks 28 and bifurcates 
the engine 12. The vertical axis V about which the crankshaft 16 rotates 
desirably lies within the central plane A. 
Each cylinder bank 28 includes a plurality of parallel cylinder bores 30. A 
cylinder liner (not shown) forms each cylinder bore 30. The cylinder liner 
is cast or pressed in place in the cylinder bank 28. As is typical with 
V-type engine arrangements, the cylinder bores 30 of the first cylinder 
bank 28 are offset slightly in the vertical direction from the cylinders 
bores 30 of the second cylinder bank 28 so that the connecting rods of 
adjacent cylinders can be journalled on the same throw 32 of the 
crankshaft 16, as known in the art. 
As understood from FIG. 4, each cylinder includes a plurality of scavenge 
passages 34, 36 formed in the cylinder block. In the illustrated 
embodiment, each cylinder includes a main scavenge passage 34 and a pair 
of circumferentially disposed side scavenge passages 36. The scavenge 
passages 34, 36 terminate in respective scavenge ports formed in the 
cylinder liner. 
An exhaust passage 38 communicates with the cylinder bore 30 through an 
exhaust port. The exhaust port is formed in the cylinder liner and 
desirably lies diametrically opposite of the main scavenge port and 
between the side scavenge ports. The configuration of the ports desirably 
is designed to provide a Schnurle-type scavenging in the cylinder. 
The exhaust passages 38 associated with the cylinders of each cylinder bank 
28 lead away from the respective cylinder and merge into an exhaust system 
(not shown). The exhaust system discharges engine exhaust from the 
outboard motor 14 in a conventional manner. 
As seen in FIGS. 3 and 4, a piston 42 reciprocates within each cylinder 
bore 30. Connecting rods 44 link the pistons 42 to the crankshaft 16 so 
that reciprocal linear movement of the pistons 42 rotate the crankshaft 16 
in a known manner. The crankshaft 16 rotates about the vertical axis V. 
The crankshaft includes a plurality of spaced rod journals 32 which lie 
off axis from the crankshaft 16. An end of one of the connecting rods 44 
is coupled to the rod journal 32 so as to link the corresponding piston 42 
to the crankshaft 16 in a known manner. 
A cylinder head assembly 46 is affixed to each of the cylinder banks 28 by 
conventional fasteners. Each cylinder head assembly 46 includes a 
plurality of recesses 48. One recess 48 cooperates with each cylinder bore 
30 to close an end of the cylinder. The recess 48 in the cylinder head 46 
and the corresponding cylinder bore 30 and piston 42 together define a 
variable volume chamber which, at minimum volume, defines the combustion 
chamber. 
Spark plugs 50 are mounted in the cylinder head assemblies 46. A spark gap 
of each spark plug 50 lies generally at the center of the corresponding 
recess 48 of the cylinder head 46; however, the spark plug 50 can have 
other positions and orientations in the combustion chamber in order to 
improve stratification of the fuel charge about the spark gap of the spark 
plug 50, as known in the art. An ignition system 52 (FIG. 4) fires the 
spark plugs 50, as described below. 
As seen in FIGS. 3 and 4, a skirt 54 of the cylinder block assembly 26 and 
a crankcase member 56 (not shown) cooperate to form the crankcase. The 
crankcase is divided into a plurality of chambers 58, with each chamber 58 
communicating with a respective cylinder bore 30 through the corresponding 
scavenge passages 34, 36. Adjacent crankcase chambers 36 are sealed from 
each other. 
As best illustrated in FIGS. 4 through 6, an induction system which 
communicates with each crankcase chamber 58. In the illustrated 
embodiment, the induction system includes a plurality of throttle devices 
60 to control the air flow into the engine 12. The throttle devices 60 
desirably correspond in number to the number of crankcase chambers 58. 
Each throttle device 60 is dedicated to control air flow in a respective 
crankcase chamber 58. 
The throttle devices 60 can, for example, be throttle valve assemblies; 
however, other conventional throttle devices can be used to regulate air 
flow into the crankcase chambers 58. Each throttle assembly 60 includes a 
throttle body 62 which houses at least one throttle valve 64. A throttle 
shaft 66 supports the valve 64 within a throttle passage 68 defined within 
the throttle body 62. 
In the illustrated embodiment, as best understood from FIGS. 5 and 6, a 
throttle body 62 includes two adjacent throttle passages 68. A throttle 
valve 64 operates within each passage 68 and a single throttle shaft 66 
passes through both the passages 68 and supports the respective valve 64 
within each passage 68. 
Each throttle valve passage 68 communicates with an intake silencer 70 of 
the induction system. The intake silencer 70 includes a plurality of 
inlets 72 positioned to the sides of the throttle bodies 62. The inlets 72 
open into a plenum chamber 74 which communicates with each of the throttle 
passages 68 of the throttle devices 60. 
A throttle linkage (not shown) desirably connects the throttle shafts 66 
together so as to uniformly and simultaneously operate and control the 
throttle valves 64 in a known manner. Inlet air flow through the plenum 
chamber 74 and passes through each throttle device 60 when the linkages 
rotates the corresponding throttle shaft 66 to open the throttle valve 64. 
Each throttle passage 68 communicates with a respective intake passage 76 
formed in an intake manifold 78. The intake 76 passage in turn 
communicates directly which a corresponding crankcase chamber 58. 
In the illustrated embodiment, as best understood from FIGS. 5 and 6, the 
inlets to an adjacent pair of intake passages 76 lie next to each other 
and communicate with the corresponding throttle passage 68. One of the 
intake passages 76 of the pair extends below the other passage 76 to 
communicate with the crankcase chamber 58 immediately beneath the 
crankcase chamber 58 with which the upper passage of the pair 
communicates. In this manner, the inlets to the adjacent pair of intake 
passages 76 lie at the same level, while the outlet of the intake passages 
76 lie at different level so that each passage communicates with one of 
two crankcase chambers 58 which are arranged one above the other. FIG. 6 
best illustrates the overlapping layout of the corresponding pairs of 
intake passages 76 of the intake manifold 78. 
Each intake passage 76 delivers the fuel/air charge to the respective 
crankcase chamber 58 through a read-type check valve 80 connected to the 
intake manifold 78. The read-type check valve 80 permits air to flow into 
the crankcase chamber 58 through an inlet channel 82 defined by the 
crankcase member 56 when the corresponding piston 42 moves toward top dead 
center (TDC), but precludes reverse flow when the piston 42 moves toward 
bottom dead center (BDC) to compress the charge delivered to the crankcase 
chamber 58. 
The reed-type check valves 80 are mounted to a support plate 83 that lies 
between the intake manifold 78 and the crankcase member 56. As seen in 
FIG. 6, each reed-type check valve 80 includes a mounting cage 84 that 
generally has a V-shape configuration. An apex edge of each mounting cage 
generally lies parallel to the rotational axis V of the crankshaft 16. 
Reed-type valve plates 86 are affixed to opposite sides of the cage 84 in 
a suitable manner with the down-stream ends of the valve plates 86 able to 
move relative to the cage 84. Stopper plates 88 lie to the outside of the 
valve plates 86 to limit the opening degree of the valve plates 86, as 
known in the art. 
With reference to FIGS. 4 and 5, at least one fuel injector 90 injects fuel 
into the air stream passing through each intake passage 76. In the 
illustrated embodiment, the intake manifold 78 includes at least one boss 
92 associated with each intake passage 76 on one side of the manifold 78. 
Each boss 92 receives a fuel injector 90. The boss 92 supports the fuel 
injector 90 so that a spray axis of the fuel injector 90 generally aligns 
with the center of the bight of the valve cage 84. In this manner, the 
fuel injector 90 sprays fuel toward the center of the valve 80 to 
facilitate uniform mixture of the fuel/air charge passing through the 
valve 80. 
Each fuel injector 90 includes a solenoid winding 94 which is energized in 
the manner described below. When energized, the fuel injector 90 injects 
fuel into the air stream passing through the intake passage 76 in the 
intake manifold 78. 
With reference to FIGS. 4, 7 and 8, a fuel supply system 95 delivers fuel 
to each fuel injector 90. The fuel system 95 includes a fuel tank 96 (FIG. 
4) which is provided externally of the outboard drive 14, normally within 
the hull of the watercraft. A fuel transport subsystem 98 of the fuel 
supply system 95 supplies fuel to a fuel bowl 100 positioned within the 
cowling 15 of the outboard motor 14 which surrounds the engine 12. 
A plurality of low-pressure pumps 104 of the fuel transport subsystem 98 
draw fuel from the external fuel tank 96, through a conduit 106 and 
through a fuel filter 108. The fuel filter 108 separates water and other 
contaminates from the fuel. The low-pressure fuel pumps 104 supply fuel to 
the fuel bowl 100 of a vapor separator 110. 
The vapor separator 110 separates fuel vapor and other gases from the 
liquid fuel within the fuel bowl 110, as explained below in detail. As 
seen in FIG. 4, gaseous vapors flow from the fuel bowl 100, through a 
conduit 112, and into a canister 114. A pressure-relief valve 116 in a 
discharge conduit opens 118 once the pressure of the fuel vapors within 
the canister 114 reach a preselected level. With the relief valve 116 
opened, the fuel vapor flows through the conduit 118 and discharges into 
at least one of the intake passages 76 of the intake manifold 78 
downstream of the corresponding fuel injector 90. 
A high-pressure fuel delivery subsystem 120 supplies fuel to the fuel 
injectors 90 of the induction system. A high-pressure fuel pump 122 draws 
fuel from the fuel bowl 100 of the vapor separator 110 and pushes the fuel 
through a fuel filter 124. The high-pressure pump 122 desirably has at 
least two speeds in order vary the fuel flow rate through the delivery 
subsystem 120, as described below. 
A conduit 126 connects the high-pressure pump 122 to a fuel rail or 
manifold 128 with the fuel filter 124 positioned within the conduit 126 
between the pump 122 and fuel rail 128. The pump 122 delivers fuel under 
high pressure through the conduit 126 to the fuel rail 128. A check valve 
130 (FIG. 8) is disposed in the conduit 126 upstream of the filter 124 to 
prevent a back-flow of fuel from the fuel rail 128. 
The fuel rail 128 has an elongated shape and is vertically disposed. A 
lower inlet port 132 of the fuel rail 128 communicates with the conduit 
126 carrying fuel from the high pressure pump 122. The inlet port 132 
opens into a manifold chamber 134 which extends along the length of the 
fuel rail 128. 
The fuel rail 128 delivers fuel to each fuel injector 90. For this purpose, 
the manifold chamber 134 communicates with a plurality of supply ports 
defined along the length of the fuel rail 128. As best understood from 
FIG. 5, each supply port receives an inlet end 136 of the corresponding 
fuel injector 90. The supply port communicates with an inlet port to the 
fuel injector 90 to supply the fuel injector 90 with fuel. 
With reference to FIG. 4, a fuel return line 138 extends between an outlet 
port 140 of the fuel rail 128 and the fuel bowl 100 of the vapor separator 
110. The return line 138 complete a flow loop defined by the high-pressure 
fuel delivery subsystem 120 to generally maintain a constant flow of fuel 
through the fuel rail 128. The constant fuel flow through the fuel 
delivery subsystem 120 inhibits heat transfer to the fuel and thus reduces 
fuel vaporization within the fuel rail 128. The vertical orientation also 
facilitates separation of any fuel vapor which occurs within the fuel 
delivery subsystem 120 from the fuel flow into the injectors 90. 
A pressure regulator 142 desirably lies within the fuel loop, as 
schematically illustrated in FIG. 4. The pressure regulator 142 generally 
maintains a uniform fuel pressure at the injectors 90 (e.g., 50-100 atm). 
The regular 142 regulates pressure by dumping excess fuel back to the 
vapor separator 110, as known in the art. In the illustrated embodiment, 
the pressure regulator 142 is integrally formed with the fuel rail 128, 
between the manifold chamber 134 and the outlet port 140. 
FIGS. 3, 7 and 8 best illustrate the arrangement of the components of the 
fuel supply system 95 within the cowling 15. As seen in FIG. 3, the fuel 
transport subsystem 98 generally lies on one side (e.g., the left side) of 
induction system and the fuel delivery subsystem 120 generally lies on the 
other side (e.g., the right side). In the illustrated embodiment, the a 
flexible fuel intake conduit 144 connects to a conventional quick-connect 
coupling 146 positioned at the front-left side of the cowling 15. An 
internal conduit 106 connects the coupling 146 to the fuel filter 108 to 
place the filter 108 in communication with the fuel intake conduit 144. 
As seen in FIG. 7, the internal conduit 106 attaches to an inlet port on an 
upper side of the filter 108. On output line 148 connects an outlet port 
on the filter 108 to pump manifold 150. The line 148 communicates with the 
pump manifold 150 at a point proximate to an influent port of the lowest 
positioned low-pressure pump 104 to inhibit the occurrence of a vapor lock 
within the system 10, as known in the art. 
The manifold 150 communicates with the influent port of each of the 
low-pressure pumps 104. In the illustrated embodiment, the fuel transport 
subsystem 98 includes three electric low-pressure pumps 104 run by an 
electrical system of the outboard motor 10. The pumps 104 are arranged 
above one another on the side of the crankcase member 56. As best seen in 
FIG. 5, each pump 104 is mounted to a boss 152 formed on the side of the 
crankcase member 56. 
With reference to FIGS. 3 and 7, a delivery conduit 154 connects an 
effluent port of the lower-most transport pump 104 to the fuel bowl 100 of 
the vapor separator 110. Conduit segments coupled to T-fittings connect 
the effluent ports of the upper transport pumps 104 to the delivery 
conduit 154 to deliver fuel to the fuel bowl 110. 
The delivery conduit 154 extends up the side of the crankcase member 46 and 
extends around the front end of the engine 12, passing over the upper 
throttle body 62 of the induction system. The deliver conduit 154 connects 
to the fuel vapor separator 110 on the other side of the induction system. 
As seen in FIG. 8, the delivery conduit 154 extends behind the fuel rail 
128 and connects to an inlet port 156 of the vapor separator 110. The 
inlet port 156 lies on the upper side of the vapor separator 110. 
In the illustrated embodiment, the vapor separator 110 and high-pressure 
pump 122 lie within an integral housing 158 which is attached to the 
engine block assembly 26 and crankcase member 56. Bolts passing through 
flanges 160 of the housing 158 secure the housing 158 to the engine 12. 
With reference to FIG. 9, the housing 158 defines an inner cavity 162 which 
defines the fuel bowl 100 of the vapor separator 110. The housing 158 also 
houses the high-pressure pump and motor assembly 122. The slopped bottom 
surface 164 of the housing 158 funnels the fuel toward an influent port 
166 of the pump 122 positioned generally at the bottom of the fuel bowl 
100. 
The housing 158 defines the inlet port 156, a return port (not shown), a 
vapor discharge port 168 and an outlet port 170. The outlet port 170 
directly communicates with an effluent port 172 of the high-pressure pump 
122. The vapor discharge port 168 is positioned to the side of the inlet 
port 156 at a position proximate to an upper end of the housing 158. The 
vapor discharge port 168 communicates with the conduit 112 leading to the 
canister 114, and the outlet port 170 communicates with the conduit 126 
leading to the fuel rail 128. 
The inlet port 156 connects to the delivery conduit 154 extending from the 
low pressure pumps 104. A needle valve 174 operates at a lower end of the 
inlet 156 to regulate the amount of fuel within the fuel bowl 100. A float 
176 within the fuel bowl 100 actuates the needle valve 174. The float 
includes a buoyant body 178 supported by a pivot arm 180. The pivot arm 
180 is pivotably attached to an inner flange 182 within the housing 158 at 
a point proximate to the lower end of the housing inlet 156. The pivot arm 
180 also supports the needle valve 174 in a position lying directly below 
a valve seat 184 formed at the lower end of the inlet 156. Movement of the 
pivot arm 180 causes the needle valve 174 to open or close the inlet 156 
by either seating against or moving away from the valve seat 184, 
depending upon the rotational direction of the pivot arm 180. 
When the fuel bowl 100 contains a low level of fuel, the float 178 lies in 
a lowered position (as represented in phantom lines in FIG. 9). In the 
lowered position, the needle valve 104 is opened and fuel flows from the 
low pressure pumps 104, through the delivery conduit 154 and into the fuel 
bowl 100 through the inlet port 156. When the fuel bowl contains a 
preselected amount of fuel, the float 178 rises to a level where it causes 
the needle valve 104 to seat against a valve seat 184 at the lower end of 
the inlet port 156. The preselected amount of fuel desirably corresponds 
to an amount of fuel that would not fill the fuel tank above the vapor 
discharge port 168 when the outboard motor is in its tilt-up position. 
Line L in FIG. 9 represents the fuel level in the fuel bowl 100 when the 
outboard motor 14 lies in its tilt-up position. 
The high pressure pump 122 draws fuel into its influent port 166 through a 
fuel strainer 186 which lies generally at the bottom on the fuel bowl 100. 
The pump 122 can be driven in any know manner, such as, for example, by an 
electric motor (as illustrated) or directly by the engine output shaft. In 
the illustrated embodiment, the electrical contacts 188 to the motor lie 
outside the fuel bowl 100. A seal 190 also seals the electronics of the 
motor from the vapors in the fuel bowl 100. 
With reference to the schematic illustration of FIG. 4, an electronic 
control unit 192 (ECU) controls the operation of the engine 14. That is, 
the ECU 192 controls the fuel injection (both timing and duration), 
ignition timing, and the fuel flow rate through the high-pressure delivery 
subsystem 120 of the fuel delivery system 10, as explained below. The ECU 
192 also can control other engine functions, as known in the art. 
The ECU 192 communicates with a sensory system which detect a number of 
engine and ambient conditions. In the illustrated embodiment, the sensory 
system detects air flow into the engine. For this purpose, the sensory 
system includes a crankcase pressure sensor 194 and a crankcase angle 
position sensor 196. The crankshaft angle detector 196 measures the crank 
angle of the crankshaft 16 and generates an input signal indicative to the 
crank angle. The crankcase chamber pressure sensor 194 measures the 
pressure within the respective crankcase chamber 58 and generates an input 
signal indicative of the pressure. Based on this information, the ECU 192 
can arcuately determine the air flow into the engine 14 by measuring the 
pressure within a crankcase chamber 58 with the crankshaft 16 at a 
particular crank angle, and can calculate the necessary fuel amount to 
maintain the desired fuel air ratio for the current operation condition of 
the engine 14. 
A throttle angle detector 198 detects the opening degree of the throttle 
device 60 (e.g., the angular orientation of the throttle valve) and 
generates an input signal indicative of the throttle opening degree. 
An temperature sensor 200 positioned in the intake passage for each 
cylinder senses the temperature of intake air flowing into the crankcase 
chamber 58. The temperature sensor 200 generates an input signal 
indicative of the temperature of the intake air into the crankcase chamber 
58. 
A pressure sensor 202 and a knock sensor 204 are mounted to the cylinder 
head assembly 46 and the cylinder block assembly 26, respectively. The 
pressure sensor 202 measures the pressure within the combustion chamber 
and generates an input signal indicative of the sensed pressure. The knock 
sensor 204 sensors if the engine begins to knock (i.e., detonate or ping) 
and generates an input signal which indicates the presence of this 
condition, as known in the art. The ECU 192, in response, retards spark 
timing unit the knock stops. 
The sensory system can also includes sensors which detect several other 
operating characteristics of the engine 12. For instance, a back pressure 
sensor 206 measures exhaust back pressure. Although not illustrated, this 
sensor can be mounted in an expansion chamber within the drive shaft 
housing 20. The back pressure sensor 206 generates an input signal 
indicative of the sensed back pressure. 
An engine temperature sensor 208 determines the engine temperature. The 
sensor 208 generates an input signal indicative of the engine temperature 
under the operating state. 
A trim angle sensor 210 is provided adjacent the trim pin 212 to provide an 
input signal indicative of the trim angle of the outboard motor 14. 
A transmission sensor 214 determine the operational condition of the drive: 
e.g., forward, neutral or reverse. The sensor 214 produces an input signal 
which indicates the condition of the transmission as to whether the 
transmission is in a neutral or a driving condition. 
In addition to the above operational conditions, the sensory system can 
also determine several ambient conditions, such as atmospheric air 
pressure and inlet water temperature. A temperature sensor 216 measures 
the temperature of the cooling water drawn into the outboard motor 14 from 
the body of water in which the watercraft is operated. The cooling water 
is circulated through the cooling system of the engine 12 and is then 
returned to the body of water in any of a variety of conventional manners. 
The ECU 192 communicates with the sensors and receives input signals from 
them. The ECU 192 includes a fuel injection controller. In response to the 
input signals, the fuel injection controller generates an appropriate 
output signal to control the fuel injection amount and the fuel injection 
timing of the fuel injectors 90. The controller also varies the pump speed 
of the high-pressure pump 122 depending upon the operational condition of 
the engine. 
A throttle controller of the ECU 192 also receives input signals from the 
sensors. Based on the input information, the throttle controller controls 
the opening degree of the throttle devices 60. The throttle controller 
produces an output signal which is received by the throttle actuator (not 
shown) that operates the throttle shafts 66. 
The ECU 192 also includes an ignition controller which likewise receives 
the input signals from the sensors. The ignition controller controls 
ignition timing and produces an output signal received by the ignition 
system 52 which causes the spark plugs 50 to fire in a known manner. 
As seen in FIG. 4, the ignition system 52 includes a capacitor discharge 
ignition circuit 218 (CDI) which is charged by the output of a convention 
charging coil (not shown). The discharge of a CDI capacitor generated 
voltage in an ignition coil 220 associated with the spark plug 50, which 
fires in a well known manner. 
The ECU 192 controls the capacitor discharge ignition circuit 218 and the 
firing of the spark plugs 50. The ECU 192 also controls the fuel injectors 
90 to designate both the beginning and the duration of fuel injection and 
the regulated fuel pressure by adjusting the speed of the high-pressure 
pump 122. The ECU 192 can operate on any known strategy for the spark 
control and fuel injection control. 
In addition to these control features, the engine 12 can include a feedback 
control system through which the ECU 192 controls the fuel air ratio in 
response to the measurement of the actual fuel air ratio by a combustion 
condition sensor 222, such as an oxygen (O.sub.2) sensor. 
The engine 12 desirably includes an electrical system which generates 
electricity used by the engine 12 to charge and fire the spark plugs 50, 
as well as by other electrical accessories of the watercraft. For 
instance, the electrical system supplies electricity to the motors of the 
fuel pumps 104, 122 to drive the motors, to the control system to power 
the ECU 192, to the ignition system to charge the spark plugs 50, and to a 
battery for recharging. 
The electrical system includes a generator 224 for this purpose. As used 
herein, the term "generator" means a device which produces an electrical 
charge (i.e., voltage), including, for example, a DC-type generator and an 
AC-type generator (known as an alternator). In the illustrated embodiment, 
the electrical system employs an alternator to produce alternating 
electrical current. 
With reference to FIGS. 10 and 11, the alternator 224 desirably is 
supported on the side of the engine 12, proximate to the crankcase member 
56. In the illustrated embodiment, the alternator 224 lies adjacent to the 
crankcase member above the fuel vapor separator 110. As seen in FIG. 10, 
at least a portion of the alternator 224 lies beneath a portion of a 
flywheel 226 of the engine 12, and more particularly, beneath a portion of 
a ring gear 228 of the flywheel 226. The flywheel 226 is attached to the 
crankshaft 16 toward an upper end of the crankshaft 16. In this position, 
the alternator 224 lies within a recessed portion on the engine's side 
which is defined between the crankcase member 56 and the induction system 
(i.e., the intake manifold 78, throttle bodies 62 and intake silencer 70). 
The perimeter size or girth of the engine 12 is reduced with the 
alternator 224 mounted to the side of the engine 12 in this position. 
The crankshaft 16 drives the alternator 224 through a drive mechanism. In 
the illustrated embodiment, the drive mechanism comprises a pulley system; 
however, other drive mechanisms can be used to transfer power from the 
crankshaft 16 to the alternator 224, as will be readily apparent to those 
skilled in the art. 
A drive pulley 230 (i.e., a crankshaft pulley) of the pulley system is 
attached to an upper end of the crankshaft 16. In the illustrated 
embodiment, the drive pulley 230 lies above the flywheel 226 which is 
attached to the crankshaft 16 in a conventional manner. The drive pulley 
230 desirably has a diameter smaller than the diameter of the flywheel 
226. 
The alternator 224 includes a driven pulley 232 attached to a rotor shaft 
234 (FIG. 11) of the alternator 224. Rotation of the pulley 232 causes the 
alternator rotor (not shown) to spin within the stator assembly (not 
shown) of the alternator 224, as known in the art. As the rotor spins 
inside the alternator 224, an alternating magnetic polarity is produced, 
which generates AC current. 
The driven pulley 232 of the alternator 224 has a substantially smaller 
diameter than the drive pulley 230. The ratio between the diameter sizes 
of drive pulley 230 and the driven pulley 232 produces a desired spin rate 
(i.e., rotational speed) of the alternator 224. For example, the diameter 
of the drive pulley 230 is about 3 times larger than the diameter of the 
driven pulley 232, such that the alternator rotor shaft 234 rotates at 
about 3 times the rotational speed as the crankshaft 16. 
As seen in FIG. 10, an intermediate compound pulley assembly 236 operates 
between the drive pulley 230 and the driven pulley 232. The compound 
pulley assembly 236 includes an upper and lower pulleys 238, 240 supported 
by an intermediate shaft 242. The shaft 242 rigidly connects together the 
upper and lower pulleys 238, 240, such that both pulleys 238, 240 rotate 
together at the same speed. 
In the illustrated embodiment, the upper and lower pulleys 238, 240 have 
about the same diameter size as that of the driven pulley 232. The 
intermediate compound pulley assembly 236 therefore rotates at the same 
rotational speed as the driven pulley 232; however, those skilled in the 
art will appreciate that the sizes of the pulleys of the intermediate 
compound pulley assembly 236 can designed to increase the speed at which 
the driven pulley 232 rotates. 
The shaft 242 lies generally parallel to the vertical axis V of the 
crankshaft 16 and to a rotational axis of the alternator rotor shaft 234. 
As best seen in FIG. 11, a support carrier 244, which is connected to the 
cylinder block assembly 26, supports a lower end of the intermediate shaft 
242. The lower end is journaled within an aperture of the support carrier 
244, and is releasably connected to the support carrier 244 to prevent 
axial movement of the shaft 242 relative to the support carrier 244. The 
coupling between the support carrier 244 and the shaft 242 maintains the 
shaft 242 in the desired generally vertical orientation. 
As seen in FIG. 10, the shaft 242 lies beyond the peripheral edge of the 
ring gear 228. In the illustrated embodiment, the shaft position also 
places the upper and lower pulleys 238, 240 beyond the peripheral edge of 
the ring gear 228; however, the position of the shaft 242 or the size of 
the pulleys 238, 240 can be changed such that one or both of the upper and 
lower pulleys 238, 240 overlap, either above or beneath, a portion of the 
ring gear 228. In this position, the shaft 242 lies at a distance L1 from 
the vertical axis V of the crankshaft 16 (i.e., the rotational axis of the 
drive pulley 230) and a distance L2 from the rotational axis of the 
alternator rotor shaft 234. The distance L1 between the axis of crankshaft 
16 and the intermediate shaft 242 is greater than the distance L2 between 
the rotor shaft 234 and the intermediate shaft 242. 
An upper belt couples the upper pulley 238 of the compound pulley assembly 
236 to the drive pulley 230, and a lower belt 248 couples the lower pulley 
240 of the pulley assembly 236 to the driven pulley 232. In the 
illustrated embodiment, as seen in FIG. 10, the belts 246, 248 are ribbed 
V belts with longitudinal ribbing on the undersides of the belts 246, 248. 
The grooves of the pulleys 230, 232, 238, 240 have corresponding shapes to 
cooperate with the belts 246, 248. 
As seen in FIG. 10, the upper belt 246 has a longer length that the lower 
belt 248 due to the differences in pulley sizes and to the differences in 
distances L1, L2 between the crankshaft 16 and the intermediate shaft 242, 
and the alternator rotor shaft 234 and the intermediate shaft 242. As seen 
in FIG. 10, the upper belt 246 desirably has a minimum thickness within 
acceptable engineering limits and standard sizes in order to minimize the 
height of the pulley assembly above the flywheel 226. In this manner, the 
overall height of the engine 12 is reduced in comparison to prior engine 
designs. 
In the illustrated embodiment, the upper belt 246 has a thinner width than 
the lower belt 248. The lower belt 248 can have a larger width because the 
width of the belt 248 at this location does not effect the overall height 
of the engine 12. 
As understood from FIG. 10, the support carrier 244 and the intermediate 
shaft 242 are coupled to the engine 12 in a manner allowing the 
intermediate pulley assembly 236 to move in direction a. Movement of the 
intermediate pulley assembly 236 in direction a increases the lengths of 
the distances L1 and L2 between the intermediate shaft 242 and the 
crankshaft 16, and between the intermediate shaft 242 and the alternator 
rotor shaft 234. In this manner, the intermediate pulley assembly 236 also 
acts as a belt tensioner to place both belts 246, 248 in tension and to 
facilitate replacing the belts 246, 248. The support carrier 244 also can 
be spring biased to maintain tension on the belts 246, 248 and prevent the 
belts 246, 248 from slipping on the pulleys. 
The movable coupling between the support carrier 244 and the cylinder block 
assembly 26 can be accomplished in any of a variety of ways well known to 
those skilled in the art. For instance, the support carrier 244 can be 
supported by a bracket or arm which includes an elongated slot which 
extend in direction a (FIG. 10). A fastener can secure the support carrier 
244 to the bracket, which in turn is rigidly attached to the cylinder 
block 26. By loosening the fastener, the support carrier 244 can be moved 
over the bracket along the travel path defined by the longitudinal slot. 
As understood from FIG. 10, the amount of space required for operation of 
the tensioner is substantially less than that required in prior engine 
layouts, such as that illustrated in FIG. 1. The direction of movement of 
the support carrier 244 extends along the fore side of the corresponding 
cylinder bank 28. The support carrier 244 thus principally moves within 
the space necessary to housing the cylinder block assembly 26. Unlike 
prior engine layouts, no additional space is required within the cowling 
to allow for adjustments of the pulley belts. 
As seen in FIG. 10, the alternator 224 and the compound pulley assembly 236 
lie on one side of the central plane A of the engine 12 and a starter 
motor 250 lies on the other side. The starter motor 250 is positioned to 
engage a pinion gear 252 of the starter motor 250 with the ring gear 228 
on the flywheel 226. This arrangement of these engine components minimizes 
the width of the engine 12 at its upper end. The arrangement also 
streamlines the shape of the cowling 15 surrounding the engine 12. 
Although this invention has been described in terms of a certain preferred 
embodiment, other embodiments apparent to those of ordinary skill in the 
art are also within the scope of this invention. Accordingly, the scope of 
the invention is intended to be defined only by the claims that follow.