Marine propulsion device with an improved lubricant management system

A four-cycle internal combustion engine is provided with a scavenge pump and a pressure pump that are both attached for rotation to a crank shaft of the engine. The inlets and outlets of the scavenge pump and pressure pump are located at positions within the structure of the internal combustion engine which inhibits the drainage of lubricant from a lubricant reservoir to the engine when the outboard motor is either tilted at an extreme angle from vertical or stored in a horizontal position. The scavenge pump and the pressure pump can be gerotor pumps and can either be located proximate each other at one side of the engine or displaced from each other on opposite sides of the engine.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is generally related to a marine propulsion device 
and, more particularly, to an outboard motor with a lubricant management 
system that maintains a dry sump and a lubricant reservoir by utilizing 
two pumps which are both driven by the crank shaft of an internal 
combustion engine. 
2. Description of the Prior Art 
As is known to those skilled in the art, outboard motors which use 
four-cycle internal combustion engines present certain problems that are 
not inherent with two-cycle engines. Since four-cycle engines are, by 
their nature, larger than two-cycle engines of equivalent horsepower, the 
location of the sump requires particular care. For example, if the sump of 
the internal combustion engine is used to store the oil of the engine, 
placement of the sump within the crank shaft housing creates a particular 
problem because it places the oil close to the exhaust passages. This can 
create excessive temperatures in the oil within the sump and generally 
requires a cooling water system to maintain the oil temperature within 
acceptable magnitudes. If the sump is placed directly under the internal 
combustion engine and above the crank shaft housing, a four-cycle internal 
combustion engine would typically extend too high to be practical. In 
other words, the internal combustion engine and its cowling would extend 
significantly above the point about which the engine is intended to be 
rotated for trimming. If, on the other hand, the sump is located on the 
sides of the engine, it would be too wide and would likely obscure the 
boat operator's vision in the aft direction. 
To solve these problems, it is well-known to those skilled in the art to 
provide the four-cycle internal combustion engine with a dry sump in 
combination with a lubricant reservoir. Oil that drains into the sump, 
under the influence of gravity, is pumped by a scavenge pump into the 
reservoir for future use. Another pump, referred to as a pressure pump, 
draws the lubricant from the reservoir and transmits it through a conduit 
to regions that require lubrication within the structure of the internal 
combustion engine. These principles are generally wellknown to those 
skilled in the art. 
U.S. Pat. No. 4,523,556, which issued to Suzuki on Jun. 18, 1985, discloses 
a four-cycle internal combustion engine for outboard motors. Two 
embodiments of the lubricating system for four-cycle engines are 
described. Each of the systems embodies a lubricant sump that is disposed 
beneath the engine and to which lubricant is returned by gravity. In each 
of the two embodiments, a buffer volume is provided which receives 
lubricant when the engine is oriented in other than a desired position so 
that the oil will flow into the buffer volume rather than being discharged 
from the sump. The lubricant is returned to the engine from the buffer 
volume when the engine is again placed in its normal orientation. In one 
embodiment of this particular system, the buffer volume is provided by the 
cam shaft chamber of the engine. 
U.S. Pat. No. 4,735,590, which issued to Mondek on Apr. 5, 1988, describes 
a lubrication system for a marine propulsion device. The marine propulsion 
device comprises a propulsion unit including an internal combustion 
engine, a pump driven by the engine, a transom bracket for mounting the 
propulsion unit to the transom of a boat, a fluid reservoir carried by the 
transom bracket, a fluid cooler carried by the transom bracket for cooling 
the fluid contained in the reservoir, and a conduit for communicating the 
cold oil to the pump. 
U.S. Pat. No. 4,828,519, which issued to Watanabe on May 9, 1989, describes 
an outboard motor with an improved lubricating system for its internal 
combustion engine. The lubricant sump is positioned beneath the engine, 
and oil is returned to the sump through a drain opening in a spacer plate 
that separates the engine from the crank shaft housing. The oil sump and 
drain opening are configured so that oil will not return from the sump 
through the drain opening to the engine when the outboard motor is laid on 
its side edge. 
U.S. Pat. No. 5,036,804, which issued to Shibata on Aug. 6, 1991, discloses 
a cooling system for a four-stroke outboard motor. The cooling system is 
used for a four-cycle internal combustion engine that is utilized as a 
power plant for an outboard motor. The cooling system is designed so that 
coolant is first delivered to cool an exhaust manifold in the cylinder 
block. Then the exhaust ports of the cylinder head and the other cylinder 
head components and then the cylinder block cooling jacket surrounding the 
cylinder bores. 
U.S. Pat. No. 5,037,340, which issued to Shibata on Aug. 6, 1991, describes 
a lubricating device for a four-stroke outboard motor. A number of 
embodiments of outboard motors powered by four-cycle internal combustion 
engines have dry sump lubrication systems wherein the external oil 
reservoir is positioned externally of the engine. In some embodiments, the 
reservoir is contained directly in the power head and in other embodiments 
the reservoir is contained externally of the outboard motor. The use of 
external positioning of the lubricant reservoirs from the crank shaft 
housing permits the use of a large expansion chamber for the exhaust 
system in the crank shaft housing. In one embodiment, a pair of expansion 
chambers are provided. 
U.S. Pat. No. 5,072,809, which issued to Shibata on Dec. 17, 1991, 
describes a lubricating device for a four-stroke outboard motor. The dry 
sump lubrication system includes a scavenge pump for drawing lubricant 
drained from the engine lubricating system through an inlet port and 
returning it to a dry sump reservoir through an outlet port and a pressure 
pump that draws lubricant from the dry sump lubricant reservoir through an 
inlet port and delivers it to the engine lubricating system through an 
outlet port. At least one of the ports of each of the pumps is positioned 
above the normal lubricant level in the lubricant reservoir when it is 
filled with the normal volume of lubricant so as to ensure that lubricant 
will not drain back into the engine when the pump system is not operating. 
Various arrangements for achieving this result and for cooling the 
lubricant system are described in U.S. Pat. No. 5,072,809. 
U.S. Pat. No. 5,149,287, which issued to Koike on Sep. 22, 1992, describes 
a separate oiling system for an outboard motor. The lubricating system for 
an outboard motor has a lubricant delivery tank mounted on the outboard 
motor which is replenished by a pumping system from a separate lubricant 
storage tank contained within the hull of an associated watercraft. The 
circuit for controlling the pump includes a trim angle sensor which is 
mounted on the lubricant delivery tank for preventing operation of the 
pump when a trim angle change would incorrectly indicate a need for the 
addition of lubricant to the lubricant delivery tank. 
U.S. Pat. No. 5,163,394, which issued to Koishikawa et. al. on Nov. 17, 
1992, describes an engine with horizontal cylinders and an outboard engine 
assembly. The engine assembly includes a cylinder block with at least one 
horizontal cylinder defined therein, an oil pan disposed downwardly of the 
cylinder block, a cylinder head coupled to the cylinder block, and a head 
cover coupled to the cylinder head. The engine assembly also includes a 
valve operating mechanism chamber defined jointly between the cylinder 
head and the head cover, a lubricating oil supply passageway for supplying 
lubricating oil from the oil pan to at least the valve operating mechanism 
chamber, and a lubricating oil return passageway for returning lubricating 
oil from at least the valve operating mechanism chamber to the oil pan. 
The lubricating oil return passageway has openings for introducing 
lubricating oil from the valve operating mechanism chamber. The openings 
are defined in inner surfaces, respectively, of the cylinder head and the 
head cover which face a bottom of the valve operating mechanism chamber. 
U.S. Pat. No. 5,215,164, which issued to Shibata on Jun. 1, 1993, discloses 
a lubricating device for a four-stroke outboard motor. The dry sump 
lubrication system includes a scavenge pump for drawing lubricant drained 
from the engine lubricating system through an inlet port and returning it 
to a dry sump reservoir through an outlet port and a pressure pump that 
draws lubricant from the dry sump lubricant reservoir through an inlet 
port and delivers it to the engine lubricating system through an outlet 
port. At least one of the ports in each of the pumps is positioned above 
the normal lubricant level in the lubricant reservoir when it is filled 
with the normal volume of lubricant so as to ensure that lubricant will 
not drain back into the engine when the pump system is not operating. 
Various arrangements for achieving this result and for cooling the 
lubricant are described in U.S. Pat. No. 5,215,164. 
U.S. Pat. No. 5,439,404, which issued to Sumigawa on Aug. 8, 1995, 
describes a cooling system for an outboard motor. The lubricating 
reservoir bends into the crank shaft housing and is surrounded by an 
opening and is surrounded by an open trough-like manifold to which cooling 
water is delivered from the engine. This manifold has lower restricted 
openings that direct the coolant to the outer peripheral wall of the oil 
pan of the lubricant reservoir. The water level is maintained by a 
weir-like structure, and the water that overflows the weir is also 
directed toward the outer surface of the lubricant reservoir. 
U.S. Pat. No. 5,640,936, which issued to Hudson on Jun. 24, 1997, discloses 
a removable oil reservoir for dry sump internal combustion engines. The 
removable oil tank and oil filter for a four-cycle dry sump internal 
combustion engine has particular utility in marine applications. A support 
for the tank is attached to or near the engine, and the oil tank is held 
in engagement with the support by mechanical quick disconnect retainers. 
Oil lines connecting the tank and the engine oil circulating system are 
connected by quick disconnect fluid connectors. One portion of the quick 
disconnect fluid connectors may be fixedly attached to a support for the 
tank in a position where they assist in supporting the oil tank when the 
connectors are joined. 
The United States patents described immediately above are hereby 
incorporated by reference herein. 
As is well known to those skilled in the art and described in the patents 
discussed above, it is common to provide a dry sump and a second lubricant 
reservoir for four-cycle internal combustion engines used in outboard 
motors. The inherently larger four-cycle engines, compared to two-cycle 
engines of similar power rating, require that the various components of 
the internal combustion engine be efficiently positioned to avoid making 
the outboard motor excessively high or wide. In addition, the lubricating 
oil must be maintained at a suitable temperature to avoid overheating or 
overcooling. The patents described above illustrate many different 
approaches known to the skilled artisan. In view of the prior art, it 
would be significantly beneficial if the scavenge pump and pressure pump 
could be advantageously located within the structure of the outboard motor 
to efficiently pump lubricant from the dry sump to the lubricant reservoir 
and from the lubricant reservoir to the regions of the internal combustion 
engine that require lubrication. It would also be significantly beneficial 
if the lubrication system could be constructed to take advantage of the 
efficiently located pressure and scavenge pumps while also avoiding the 
drainage of lubricant back into the engine when the outboard motor is 
tilted significantly from its normal operating position, either during use 
or when it is removed from a watercraft and stored. 
SUMMARY OF THE INVENTION 
A marine propulsion device made in accordance with the present invention 
comprises a power head that, in turn, comprises an internal combustion 
engine. The internal combustion engine includes a lubricating system and a 
sump into which a lubricant drains, under the influence of gravity, after 
lubricating certain preselected lubricated regions of the internal 
combustion engine. It also comprises a crank shaft that is driven by the 
internal combustion engine and is rotatably supported within a portion of 
the power head. A lubricant reservoir is provided and displaced from the 
sump for storing a buffer quantity of the lubricant. The quantity of 
lubricant in the reservoir has an upper surface location when the marine 
propulsion device is in normal use. 
The marine propulsion device also comprises a pressure pump that is 
attached for rotation to the crank shaft of the internal combustion 
engine. It has a pressure pump inlet disposed in fluid communication with 
a portion of the lubricant reservoir below the upper surface of the 
lubricant and a pressure pump outlet disposed in fluid communication with 
the preselected lubricating regions of the internal combustion engine for 
transferring the lubricant from the lubricant reservoir to the preselected 
lubricated regions. 
In addition, the propulsion device comprises a scavenge pump attached for 
rotation to the crank shaft. The scavenge pump has a scavenge pump inlet 
which is disposed in fluid communication with the sump of the internal 
combustion engine and a scavenge pump outlet disposed in fluid 
communication with the lubricant reservoir at a location above the upper 
surface of the lubricant for transferring the lubricant from the sump to 
the lubricant reservoir. 
In order to facilitate the operation of the lubrication system, a vent is 
connected between and in fluid communication with the lubricant reservoir 
and with the crankcase of the internal combustion engine. 
In one embodiment of the present invention, the pressure pump and the 
scavenge pump are disposed proximate each other at a common side of the 
internal combustion engine. In an alternative embodiment, the pressure 
pump and the scavenge pump are displaced from each other at opposite sides 
of the internal combustion engine. The choice of embodiment of the present 
invention depends on the particular application of the lubrication system. 
The marine propulsion device of the present invention is intended for use 
with a four-cycle internal combustion engine used in an outboard motor. 
The pressure pump and the scavenge pump can be gerotor pumps.

DESCRIPTION OF PREFERRED EMBODIMENT 
Throughout the description of the preferred embodiment of the present 
invention, like components will be identified by like reference numerals. 
FIG. 1 shows a side section view of an internal combustion engine used as 
the power head for an outboard motor. The view is highly schematic, and 
many parts of the internal combustion engine are intentionally not shown 
in FIG. 1 for the purpose of clarity so that the figure can more clearly 
illustrate the primary components of the present invention. The internal 
combustion engine 10, when in normal use, has a top 12, a bottom 14, a 
front 16 and a back 18. A crank shaft 20 extends vertically and rotates 
about centerline 22 in response to the operation of the internal 
combustion engine 10. A cam shaft 26 also extends vertically and rotates 
about centerline 28. The portion of the outboard motor illustrated in FIG. 
1 defines the power head. The internal combustion engine has a lubricating 
system in order to provide lubricant to preselected lubricated regions of 
the internal combustion engine. 
In FIG. 1, it should be understood that a plurality of pistons are disposed 
in the region between the crank shaft 20 and the cam shaft 26 for 
reciprocation in a horizontal direction. The crankcase of the internal 
combustion engine is located in the vicinity identified by reference 
numeral 30, and the cams, which are attached to the cam shaft 26, are 
located in the region identified by reference numeral 32. After lubricant 
is provided to the preselected lubricated regions of the internal 
combustion engine, it drains under the influence of gravity toward the 
sump at the bottom portion of the engine. Arrows D in FIG. 1 represent the 
drainage of the lubricant toward the sump. A scavenge pump 40 draws the 
lubricant from the bottom portion, or sump, of the internal combustion 
engine 10 and causes it to flow into and through conduit 42. The scavenge 
pump inlet 44 is disposed in fluid communication with the sump of the 
internal combustion engine. The scavenge pump outlet 46 is disposed in 
fluid communication with a lubricant reservoir 50 at a location above an 
upper surface 52 of a quantity of lubricant stored in the lubricant 
reservoir 50. Arrows S indicate the flow of lubricant from the scavenge 
pump inlet 44 to the scavenge pump outlet 46 under the influence of the 
scavenge pump 40. The scavenge pump 40 is rigidly attached to the crank 
shaft 20 and its rotor rotates in unison with the crank shaft. 
A pressure pump 60 causes lubricant to flow from the pressure pump inlet 
62, as represented by arrows P, to the pressure pump outlets 64 located 
proximate and in fluid communication with preselected lubricated regions 
of the internal combustion engine. For purpose of illustration, the 
pressure pump outlets 64 are shown at locations near the crank shaft 20 
and the cam shaft 26, but it should be clearly understood that many 
different outlets can be provided to lubricate a plurality of lubricated 
regions of the engine. The pressure pump 60 is attached for rotation to 
the crank shaft 20 and has a pressure pump inlet 62 disposed in fluid 
communication with a portion of the lubricant reservoir 50 below the upper 
surface 52 of the lubricant 70 within the reservoir 50. The pressure pump 
60 also has at least one pressure pump outlet 64 disposed in fluid 
communication with the one or more preselected lubricated regions of the 
internal combustion engine. The purpose of the pressure pump 60 is to 
transfer lubricant from the lubricant reservoir 50 to the preselected 
lubricated regions. 
In the embodiment shown in FIG. 1, the scavenge pump 40 and the pressure 
pump 60 are disposed proximate each other and are both attached for 
rotation to the crank shaft 20. The two pumps are disposed at a common 
side of the internal combustion engine. In other words, both of the pumps 
are at the bottom portion of the internal combustion engine and located at 
a common side with respect to the location of the pistons of the engine. 
An oil filter 80 is connected in fluid communication between the pressure 
pump 60 and its pressure pump outlets 64. 
A vent 86 is connected between the lubricant reservoir 50 and the crankcase 
region of the engine. A first end 88 of the vent 86 is disposed at a 
location within the reservoir 50 above the upper surface 52 of the 
lubricant 70. The second end 89 of the vent 86 is disposed at a region 
near the bottom of the crankcase 30. A filler cap 90 is provided to permit 
additional lubricant to be added to the reservoir 50 when needed. 
With continued reference to FIG. 1, several characteristics of the 
lubricating system should be noted. The pressure pump inlet 62 is located 
near the bottom of the reservoir 50 to assure that it is under the upper 
surface 52 even if the outboard motor is tilted at an extreme angle from 
vertical. In addition, the inlet 44 of the scavenge pump 40 is located at 
the bottom portion of the internal combustion engine in order to allow the 
oil in the sump to be drawn from the sump and transferred to the reservoir 
50. The scavenge pump outlet 46 is disposed above the upper surface 52 of 
the lubricant 70 within the reservoir 50. The first end 88 of the vent 86 
is disposed above the upper surface 52 of the lubricant 70 and the second 
end 89 of the vent 86 is disposed at the bottom region of the crankcase 
30. 
FIG. 2 is a front sectional view of the internal combustion engine shown in 
FIG. 1. The scavenge pump transfers oil to the reservoir 50 through the 
scavenge pump outlet 46 which is located above the upper surface 52 of the 
lubricant 70. The pressure pump 60 draws lubricant from the pressure pump 
inlet 62 and transfers it, as represented by arrows P, through the oil 
filter 80 and to the preselected lubricated regions of the engine. The 
vent 86 has its first end 88 disposed within the reservoir 50 to allow 
equalization of pressure between the inside of the reservoir 50 and the 
second end 89 of the vent 86 disposed within the crankcase 30. 
With reference to FIGS. 1 and 2, it can be seen that the first end 88 of 
the vent 86 is located at the upper right corner of the reservoir 50 in 
FIG. 2 and near the front 18 of the reservoir 50 in FIG. 1. Furthermore, 
the second end 89 of the vent 86 is shown at the lower left corner of the 
reservoir 50 in FIG. 2 and at a position toward the right of the reservoir 
50 in FIG. 1. As will be described in greater detail below, the 
configuration of the vent 86 is useful in avoiding inadvertent draining of 
lubricant from the reservoir 70 into the engine when the outboard motor is 
stored or tilted at an extreme angle from vertical. 
FIG. 3 is a section view of FIG. 1. In FIG. 3, reference numeral 142 
represents the scavenge pump inlet from the cylinder head region of the 
engine, and reference numeral 143 represents the scavenge pump inlet from 
the crankcase region 30 of the engine. Reference numeral 162 represents 
the pressure pump inlet port. 
With reference to FIGS. 1, 2 and 3, it can be seen that the vent 86 has its 
first end 88 positioned within the reservoir 50, and its second end 89 
displaced from the first end 88 by a considerable magnitude in all three 
figures. This places the first and second ends, 88 and 89, of the vent 86 
at positions so that oil will not drain from the reservoir 50 into the 
engine when the outboard motor is tilted at an extreme angle from vertical 
or stored in a horizontal position. This can be seen by imagining that the 
engine is stored in a horizontal configuration on its front 18 surface. 
The lubricant 70 would naturally settle in the front portion of the 
reservoir 50 and would likely cover the scavenge pump outlet 46 beneath 
the upper surface of the lubricant. In addition, the first end 88 of the 
vent 86 would also be below the surface of the lubricant. However, the 
scavenge pump inlet 44 would be above the upper surface of the lubricant. 
The second end 89 of the vent 86 would also be above the upper surface of 
the lubricant. Therefore, no drainage of lubricant would occur from the 
reservoir 50 into the engine compartment. If the engine 10 is stored on 
its port side 200, the upper surface of the lubricant would likely be 
above the second end 89 of the vent 86 and the scavenge pump outlet 46. 
However, the first end 88 of the vent 86 would be above the upper surface 
as would the scavenge pump inlet 44. The pressure pump inlet 62 would also 
be above the upper surface. By comparing FIGS. 1, 2 and 3 to each other, 
it can be seen that oil will not drain from the reservoir 50 to the other 
portions of the engine when the outboard motor is tilted at an extreme 
angle from vertical or stored in a horizontal position on any of its four 
sides. 
With continued reference to FIGS. 1, 2 and 3, it should be noted that dry 
sump lubricating systems require two pumps to be included within the 
system. The scavenge pump 40 transfers oil from the bottom portion of the 
sump to the lubricant reservoir 50. The second pump, the pressure pump 60, 
transfers oil from the bottom region of the reservoir 50 to various 
preselected lubricated portions of the engine. From those lubricated 
portions, the lubricant drains to the sump of the engine to be transferred 
again by the scavenge pump 40 to the reservoir 50. The embodiment of the 
present invention illustrated in FIGS. 1, 2 and 3 attaches both the 
scavenge pump 40 and the pressure pump 60 to the crank shaft 20 for 
rotation therewith. This technique avoids the need for additional power 
takeoff shafts which are connected to the crank shaft for the purpose of 
driving either one or both of the pumps. It also allows for a compact 
structure which locates both of the pumps within the internal combustion 
engine with very little use of space. Naturally, the direct attachment of 
the scavenge pump and pressure pump to the crank shaft 20 eliminates the 
need for additional shafts and gears to transmit power from the crank 
shaft 20 to the two pumps. The attachment of the two pumps directly to the 
crank shaft represents a significant improvement over the known 
arrangements for providing the scavenge pump and pressure pump for a 
four-cycle internal combustion engine used as a power head for an outboard 
motor. 
The scavenge pump 40 and pressure pump 60 illustrated in FIGS. 1, 2 and 3 
are gerotor pumps in a preferred embodiment of the present invention. 
Between the to gerotor pumps, a steel plate 300 is disposed to provide a 
fluid seal between the pumps and prevent fluid communication between the 
pressure pump 60 and the scavenge pump 40. 
FIGS. 4, 5 and 6 are analogous to FIGS. 1, 2 and 3, but show an alternative 
embodiment of the present invention. All of the components in FIGS. 4, 5 
and 6 are also present in FIGS. 1, 2 and 3, but the pressure pump 60 is 
located at the upper end of the crank shaft 22 as illustrated in FIG. 4. 
Rather than place the pressure pump 60 and the scavenge pump 40 proximate 
each other at a common side of the engine. The embodiment shown in FIGS. 
4, 5 and 6 separates the two pumps and places the scavenge pump 40 and the 
pressure pump 60 at opposite sides of the engine. This necessitates 
certain changes in the conduits used as the pressure pump inlet and 
pressure pump outlet. For example, rather than have a U-shaped inlet tube 
for the pressure pump 60 as illustrated in FIG. 2, a conventional conduit 
extends from the pressure pump into the reservoir 50 in order to locate 
the pressure pump inlet 62 at a position near the bottom of the reservoir. 
In addition, the oil filter 80 is moved to a location near the upper 
portion of the internal combustion engine which is closer to the pressure 
pump 60. As in the initial embodiment illustrated in FIG. 1, the oil 
filter 80 is located between the pressure pump 60 and the pressure pump 
outlets 64. Although conduit 320 is illustrated as having only two branch 
conduits, 61 and 62, extending from it, it should be understood that other 
branches would typically be provided for the purpose of conducting the 
lubricant to other lubricated regions of the internal combustion engine. 
Other than the differences regarding the location of the pressure pump 60 
and its related conduits, all other attributes of the present invention 
are similar in both embodiments of the present invention. 
FIG. 7 is a section view of an internal combustion engine for use with the 
first embodiment of the present invention as described above in 
conjunction with FIGS. 1, 2 and 3. FIG. 7 represents a section view of an 
engine block and cylinder head which is suitable for combination with the 
present invention. The engine block 410 has the reservoir 50 formed as an 
integral part of the engine block. In FIG. 7, centerline 22 is shown to 
represent the location where the crank shaft 20 would be supported by 
bearings 420. In addition, the pressure pump 60 would be located in region 
460 in FIG. 7, and the scavenge pump 40 would be located in region 440 in 
FIG. 7. The cylinder head 413 is attached to the engine block 410 and 
provides the locations where the valves and other components would be 
located. Pistons would be located in regions 421 and would be connected by 
connecting rods to the crank shaft 20. Valves would be disposed in regions 
423, and the cam shaft 26 would be supported in bearings 426. A cover 441 
provides protection for the cam shaft and its associated cams which would 
be aligned with the regions 423 in which the valves are disposed. 
With continued reference to FIG. 7, the space 491 is intended to allow a 
torque transmitting connection, such as a drive chain, to be made between 
the crank shaft 22 and the cam shaft 26. It also defines the sump of the 
engine. Naturally, although the present invention has been described with 
particular detail and illustrated to show two preferred embodiments of the 
present invention, alternative embodiments are also within its scope.