Power drive assembly for outboard engines

Marine power drive assemblies for converting conventional outboard engines to operate with inboard engine characteristics having horizontal drives and wherein the power heads of the conventional engines are modified by replacing the conventional adapter plates for the exhaust, water inlet and discharge for supplying coolant to the engine with modified adapter plates which both align and support a tuned exhaust expansion assembly, a gear box assembly and an engine mounting base or frame which retains the engine power head, modified adapter plate, gear box and exhaust assemblies in one combined assembly for ease of installation and/or removal from the hull of a boat. The power output of the gear box assemblies are oriented generally horizontally and are selectively connected to an appropriate propulsion source. In the preferred embodiment, the thrust source is a jet propulsion pump which is supported by the hull for power output in a substantially horizontal plane, thereby the conventional outboard engine with vertical drive is converted to a vertical engine having horizontal propulsion drive.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is generally directed to engines or power drive assemblies 
for small marine boats including water recreational vehicles, emergency 
and military supply boats and other water craft utilizing outboard engines 
ranging in size up to 375 horsepower or more and more particularly to 
power drive systems which modify outboard engines to operate with an 
inboard capability by converting the conventional vertical drive to an 
in-line horizontal drive In the preferred embodiment, conventional 
outboard engines having propeller type propulsion units are converted to 
jet or fluid propulsion systems by replacing the standard power head 
adapter plate with a combination adapter and mounting plate which will 
provided the proper interface of the power head with a tuned exhaust 
expansion assembly and a gear box assembly which will create a horizontal 
drive extending from the engine to the rear of the marine craft. Although 
the power drive assembly of the present invention may be utilized with 
various types of marine craft, the invention is disclosed as being adapted 
to a recreational boat wherein the outboard motor is mounted within the 
boat in such a manner that the entire drive train and engine are carried 
by a common support base or frame. 
2. History of the Art 
The small water craft industry has historically utilized both inboard and 
outboard engines to provide power for propulsion. Until recent years, 
propulsion was primarily established by means of impellers driven by the 
power source. In conventional outboard engines, the propellers are 
commonly mounted to the vertical drive shaft with most innovation in 
technology being directed toward modifying the drive train and changing 
impeller design and gearing. Generally, outboard engines are utilized on 
small boats and have horsepower ratings varying anywhere from 
approximately 2-375 or more horsepower. 
As the small craft industry began to develop new designs for recreational 
and other type of water vehicles such as JET SKIS and the like, 
conventional inboard engines were adapted to be utilized as the power 
source for the propulsion systems for such vehicles. In other conventional 
recreational water craft, use has been made of outboard engines which are 
mounted to the transom of the craft in such a manner that the engines may 
be swiveled to change the direction of the impeller blade to steer the 
craft or boat. As new power boats or recreational vehicles have gained 
acceptance with the boating public, new types of propulsion systems have 
been developed to improve the safety, speed, handling and overall 
performance and reliability of such boats. One such propulsion system 
incorporates the use of jet pumps to create a drive thrust. 
The development of jet pump propulsion units has enabled recreational boats 
and the like to h=driven by water thrust as opposed to mechanical 
propeller drive. Such water jet propulsion units have the advantage of not 
having any exposed rotating propeller blades associated with the 
propulsion system. Unfortunately, such jet propulsion units have required 
the redesign of conventional power and drive systems in order to make the 
use of such propulsion units possible in small craft or recreational 
boats. 
SUMMARY OF THE INVENTION 
This invention is directed to a marine power drive assembly which may be 
utilized for converting the power head mounting assembly of conventional 
outboard engines into horizontal in-line drive systems which can be used 
to power jet pump or other propulsion systems. The power drive assembly 
includes a modified adapter and mounting plate which is installed in place 
of the conventional or existing adapter plate associated with the engine 
block of an outboard engine and which adapter and mounting plate provide a 
water cooling circuit for the engine and exhaust assembly and aligns the 
exhaust outlet and power or drive output of the engine crankshaft with 
specially designed exhaust and gear box assemblies. The gear box assembly 
is carried or mounted directly to the modified adapter and mounting plate 
so as to be in proper alignment for engagement with the power output of 
the crankshaft of the engine. The gear box includes a power output which 
extends generally in horizontal alignment with the boat thereby converting 
the vertical drive of the engine to a horizontal or in-line drive wherein 
the output of the gear box is in general alignment with a propulsion 
source which is drivingly connected thereto. A tuned exhaust expansion 
assembly is also mounted to the modified adapter and mounting plate so as 
to enable exhaust from the engine to be properly discharged while being 
cooled as it is directed generally rearwardly of the water craft. The 
propulsion unit, which may vary but is shown in the preferred embodiment 
as a jet pump, is mounted to an engine base or mounting frame which is 
directly secured to the boat hull and which base frame also is secured to 
the adapter and mounting plate so as to thereby mount the engine power 
head to the boat. In use, the modified adapter and mounting plates will 
function both as the conventional adapter plates for the bottom of the 
engine blocks and also as supports for the modified drive and exhaust 
expansion assemblies. The shape of the adapter plates will be somewhat 
modified depending upon the type, size and manufacturer of an engine. 
Likewise, the exact configuration of the exhaust assemblies and engine 
mounting frames may also be varied depending upon the specifications of a 
particular engine. The gear box assembly is also designed so that the 
gearing ratios and drive input and outputs can be changed as necessary to 
accomodate specific engines and power output requirements. 
The power drive assemblies of the present invention will be described 
within the application as they are associated primarily with boats of the 
type which carry one, two or more persons on a seat or platform and 
wherein the power head of an outboard engine is used to provide power for 
the boats' propulsion systems. It should be understood, however, that the 
invention could be used to modify any type of outboard motor in any water 
craft or vehicle. That is, the power drive assembly of the present 
invention may be utilized to convert conventional outboard engines to 
engines which operate in an outboard-inboard manner where the conventional 
vertical drive is converted into a horizontal drive which may be 
selectively connected with any number of propulsion systems. The term 
outboard-inboard is descriptive of the concept of the present invention 
wherein an outboard engine is mounted inside a boat and is utilized to 
drive or power horizontally an internal, external or other propulsion 
system. 
The tuned expansion exhaust assembly of the present invention is also 
uniquely designed to both functionally and operationally cooperate and 
interface with the exhaust system of conventional outboard engine power 
heads. The exhaust expansion assembly not only provides for proper 
muffling of the engine exhaust but also cools exhaust gas emissions. The 
assembly is adapted to receive cooling water directly from the engine 
cooling system which water passes through a jacketed exhaust and muffler 
chamber to cool gases passing therethrough. The cooling water is 
subsequently introduced directly into the exhaust gas to provide 
additional cooling through contraction of the exhaust gases. 
It is the primary object of the present invention to provide a power drive 
assembly for recreational and other water craft of the type which 
conventionally use smaller outboard engines as a power source wherein the 
power source may be adapted to provide an alternate drive system to an 
in-line propulsion unit without changing the characteristics of an 
existing engine's power head. 
It is also an object of the present invention to provide power drive 
assemblies for outboard engines used with small boats wherein the outboard 
engines may be converted from vertical drives with propeller propulsion to 
horizontal drives with jet, propeller or other types of propulsion without 
major modification to either the engine's power heads or to the boats. 
It is a further object of the present invention to provide a marine power 
drive assembly which may be utilized to convert outboard engines to 
function in an outboard-inboard capacity by enabling such engines to be 
mounted within a boat and power a horizontal drive train to which any 
conventional type of propulsion unit may be drivingly connected. 
It is a further object of the present invention to enable a propeller 
driven water craft having an outboard motor ranging in power from 2-375 
horsepower to be modified to be propelled by a jet pump without 
modification to the engine's power head. 
It is another object of the present invention to increase the safety of 
various recreational and other types of water vehicles by enabling 
conventional propeller driven water craft to be powered by alternate 
propulsion systems including jet pumps. 
It is another object of the present invention to provide an alternate 
propulsion system for conventionally powered outboard motorboats whereby 
such boats may be operated utilizing jet pump thrusters for propulsion. 
It is also an object of the present invention to provide tuned exhaust 
expansion assemblies for outboard engines which are utilized in an inboard 
capacity wherein the exhaust from such engines is not only muffled but is 
cooled both indirectly by conduction and convection and directly by fluid 
injection with any backdraw of liquid being prevented by the mounting 
relationship of the exhaust assemblies with respect to the engines. 
Another object of the present invention is to provide a modified gear box 
assembly which may be utilized to convert the vertical drive of 
conventional outboard motors to an in-line horizontal drive wherein the 
gear ratio of the gear box may be selectively changed to obtain the 
optimum power output to the in-line drive system.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
With continued reference to the drawings, the marine power drive system 20 
of the present invention is shown as it is utilized with a conventional 
outboard engine E. The outboard engine is generally of the type which is 
rated between 10 and 150 horsepower but may be in the range of 2-375 
horsepower. By way of example, the power drive assembly of the present 
invention will be described as it has been used for adapting a 50 
horsepower OMC engine utilizing the modified adapter and mounting plate 
shown in FIGS. 3 and 5 and also with respect to a MERCURY 50 horsepower 
engine utilizing the modified adapter and mounting plate which is shown in 
FIGS. 6-8. It should be noted that the adapter and mounting plates shown 
in the drawings are slightly modified with respect to one another in order 
to correctly interface with the exact internal working components of each 
engine and to simultaneously function in a manner similar to the 
conventional or standard adapter plate for the engine power head. Similar 
changes may be made to the adapter and mounting plates, as will be 
discussed hereinafter, for purposes of interfacing the invention with 
other makes and sizes of engines. 
With reference to FIG. 1 of the drawings, the power drive system of the 
present invention is shown as being used with an engine power head E which 
is mounted within the body of a recreational boat RB. The engine is shown 
as being mounted generally centrally of the boat and beneath the seat S 
which is straddled by the driver. A steering mechanism M is shown as being 
mounted through the housing of the boat and is connected through 
appropriate linkage L to the propulsion system so that the nozzle thereof 
is directly pivoted in response to the movement of the steering mechanism 
as will be described in greater detail hereinafter. As shown, the engine 
is mounted generally centrally of the boat between the bow B and the stern 
N and positioned so that the bottom portion of the engine block is 
generally above the water line within the hull H. 
In preparation for modification of the vertical drive and propeller 
propulsion associated with conventional outboard engines the power head E 
is removed from the vertical drive train and housing. Thereafter, a 
specially designed or modified adapter and mounting plate, such as the one 
identified at 22 in FIG. 2, is mounted to the bottom of the power head in 
place of the conventional adapter plate. The specific details of the 
mounting plate will vary depending upon the make and model of each 
outboard motor. The specifics of two such mounting plates will be 
disclosed within the body of this application with specific references to 
FIGS. 3-5 and 6-8. The function of the modified adapter and mounting 
plates are to both seal the bottom of the engine block or power head as 
well as to provide appropriate alignment and support for a tuned exhaust 
expansion assembly 23, a gear box assembly 24 and an engine support and 
power drive alignment mounting bracket or base 25. 
With specific reference to FIGS. 2, 3, 12 and 13 of the drawings, the 
modified adapter and mounting plate 22 is secured in place to the bottom 
of the engine block or power head E by a plurality of bolts b-1 which 
extend through a plurality of openings 26 which are aligned with 
corresponding previously existing openings in the power head. Although not 
shown in the drawings, a gasket material will be placed between the engine 
and the adapter and mounting plate 22 so as to insure a fluid tight seal 
therebetween. The plate 22 includes a U-shaped slotted opening 27 which is 
of a size to receive the housing 28 of the gear box assembly 24. The gear 
box assembly is disclosed as having a power input shaft 29 extending from 
the upper portion thereof and a power output shaft 30 extending from the 
rear wall thereof. Mounting flanges 31 are provided along each of the side 
walls of the gear box and which flanges have pairs of spaced openings 32 
therein which are aligned with openings 26' adjacent the opening 27 in the 
adapter and mounting plate. After the modified adapter and mounting plate 
has been placed in position relative to the engine, the gear box is raised 
through the slotted opening 27 so that the splined end 34 of the shaft 
engages with the drive output of the engine crankshaft. In this position, 
the flanges 31 of the gear box will abut the lower wall of the adapter and 
mounting plate with the openings 32 being in alignment with the openings 
26' in the plate. Appropriate bolts b-2 are thereafter placed through the 
aligned openings to secure the gear box to the adapter and mounting plate 
and the engine block. 
The modified adapter and mounting plate not only functions to mount the 
components of the invention with respect to the engine but also provides a 
reservoir for circulating coolant or water to the engine. Each adapter and 
mounting plate includes a recessed water cooling reservoir or area 36 
which is formed in the upper portion thereof. Each reservoir is aligned 
with the water cooling system of the engine. The shape of such water 
cooling areas will therefore change depending upon the make and model of 
engine to which the adapter and mounting plate is being secured. In order 
to supply water to the engine, a fluid inlet channel 37 and a fluid outlet 
channel 38 are made intermediate the upper and lower surfaces of the 
adapter and mounting plate so as to communicate with the recessed water 
circulation reservoirs 36 formed therein. Water will be supplied to the 
reservoir 36 through the inlet 37 and cycled through the engine and 
exhausted through the outlet channel 38 in a manner which will be 
described hereinafter in greater detail. 
The adapter and mounting plate 22 also aligns the exhaust system of the 
engine with a specially tuned exhaust expansion assembly 23. The plate 
includes an exhaust opening 39 which is aligned with the engine exhaust 
and may be offset from the upper to the lower surface of the plate. The 
exhaust expansion assembly 23 includes a mounting portion 40 having an 
upper generally rectangular flange 41 which abuts the lower surface of the 
adapter and mounting plate in surrounding alignment with the exhaust 
opening 39. The flange 41 is provided with a plurality of openings 42 
through which bolts b-3 may be extended to engage with aligned openings 
which are provided in the lower surface of the adapter and mounting plate. 
As shown in the drawings, the upper flange 41 of the mounting portion 40 
of the exhaust expansion assembly is inclined with respect to the muffler 
44 of the system by way of a tapered exhaust duct 45 which communicates 
through a secondary or connector duct 46 with the muffler 44. In this 
manner, with the flange 41 secured in airtight relationship with the 
bottom of the adapter and mounting plate 22, the muffler 44 and exhaust 
pipe section 47 will be oriented at a slight downward angle toward the 
stern of the boat as shown in FIGS. 12 and 13. The connector exhaust duct 
46 also offsets the muffler 44 so that the exhaust system does not 
interfere with any of the other portions of the modified drive train of 
the power drive assembly. The exhaust assembly further includes an exhaust 
tail pipe 48 which extends outwardly through the stern of the boat so as 
to conduct the exhaust to the rear thereof 
With specific reference to FIGS. 14 and 15, the tuned exhaust expansion 
assembly 23 is specially designed to cool the exhaust gases before the 
gases are discharged from the tail pipe 48. Both the exhaust connector 
duct 46 and the muffler 44 are constructed having a double wall structure 
having inner walls 49 and 50 and outer walls 51 and 52, respectively. The 
walls create continuous fluid channels or fluid jackets 53 and 54 around 
each of the inner walls of the connector duct and muffler. The fluid 
jackets communicate with one another as shown at 55. Cooling water is 
supplied from the engine cooling system discharge 38 which is formed in 
the adapter and mounting plate 22 by way of a discharge conduit 56 and 
through inlet 57 into the connector duct 46. Therefore, the engines 
cooling system discharges directly through the exhaust expansion assembly. 
After the cooling liquid has passed through fluid jackets 53 and 54, the 
coolant will be sprayed directly into the exhaust gas passing from the 
muffler through a plurality of equally spaced openings 58 which are 
located in the upper third of the innermost end of the exhaust pipe 47. As 
the water under pressure enters the exhaust, the water will cause the 
exhaust gases to be contracted further cooling the gases as they pass 
through the tail pipe 48. It has been found that during normal operation, 
the exhaust gases are cooled from temperatures of approximately 
1250.degree. to 1300.degree. F. to 160.degree. F. as the gases pass 
through the tuned exhaust expansion assembly 23 thereby reducing the build 
up of heat within the engine compartment of the boat and also reducing the 
risk of injury from hot exhaust gases being discharged from the tail pipe 
assembly. In addition to the foregoing and as previously discussed, the 
exhaust expansion assembly 23 is mounted at an incline so that the exhaust 
pipe 47 extends downwardly or is slanted toward the stern of the boat. 
This mounting arrangement will insure that there will be no backdraw of 
water into the engine exhaust system as all water within the assembly will 
tend to flow by gravity outwardly of the tail pipe. 
After the gear box and exhaust expansion assemblies have been installed to 
the adapter and mounting plate 22, the engine's power output will be 
effectively converted to a horizontal drive through the L-shaped gearing 
achieved within the gear box. The gear box is shown in greater detail in 
FIGS. 9-11. The gear box generally includes a split housing having half 
sections 28 and 28' which are joined by a plurality of bolts 59 which 
extend through aligned openings in each of the housing sections. The input 
shaft 29 of each gear box is designed to cooperatively engage or match 
with the output of the crankshaft of the conventional engine. The length 
of the shaft may be varied depending upon the type and size of engine to 
which the box is mounted. The power input shaft is mounted within 
conventional roller bearings which are aligned with thrust bearings and 
appropriate washers and connected at its innermost end with a drive gear 
(not shown). The drive gear meshes in a spiral beveled arrangement with a 
driven gear which is carried by the inner end of the drive output shaft 
30. The output shaft is provided with appropriate roller bearings and 
seals which rotatably support the output shaft with respect to the gear 
box housing. Due to the split housing design, whenever it is necessary to 
repair the gears or if it is desired to change the gearing ratio, the 
housing sections may be easily disassembled to thereby permit access to 
the gearing elements. 
As previously discussed, an advantage of the present invention is that a 
conventional outboard engine having a propeller drive may be easily 
converted to a horizontal drive in which a jet propulsion or other type of 
propulsion or thrust source may be drivingly coupled to the engine. With 
particular reference to FIGS. 1 and 2, a jet propulsion pump 60, which may 
be of any design, is selectively coupled through flexible coupling 
elements 61 to the output shaft 30 of the gear box. The flexible coupling 
also is connected directly to the input shaft 62 of the jet pump. The 
flexible coupling assembly generally includes a pair of locking collars 63 
and 64 which are selectively receivable along the threaded ends of the 
output shaft 30 and input shaft 62 of the gear box and jet pump, 
respectively. The jet pump must be mounted in fixed relationship and in 
line with the output shaft 30 of the gear box. 
The jet pump is supported in alignment with the gear box output shaft and 
positioned at the proper level with respect to the water line adjacent the 
stern of the boat by an engine mounting bracket or base assembly 25 which 
is bolted to the boat hull. The mounting bracket or base 25 includes a 
pair of side frames 65 having openings 66 through the upper portion 
thereof which are aligned with openings 67 in the adapter and mounting 
plate 22. Appropriate bolts (not shown) are extended through the aligned 
openings 66 and 67 in order to secure the adapter and mounting plate to 
the bracket 25 to thereby secure the engine within the engine compartment 
of the boat. Each of the mounting bracket side frames includes forward 
vertical supports 68 which are taller than the rearward vertical supports 
69. Each of the side frames are connected to outwardly extending angle 
brackets 70 which have a plurality of openings 71 in spaced relationship 
along the length thereof. The pump 60 is mounted within a mounting frame 
72 having openings 73. The frame 72 is selectively aligned and secured to 
the brackets 70 with bolts extending through the aligned openings 71 and 
73. Due to the slope created by the differential heights of the front and 
rear vertical supports 68 and 69, respectively, the brackets 70 will be 
angled away from the engine E at a slope generally equal to the angle at 
which the output shaft 30 of the gear box is oriented with respect to the 
propulsion system or jet pump. 
As previously discussed, each of the adapter and mounting plates includes a 
coolant inlet passage 37 and a coolant discharge passage 38 through which 
water is supplied via water inlet line 75 and is discharged via line 56. 
The inlet line extends through the vortex side of the pump 60. During the 
operation of the pump, water will be drawn upwardly into the engine 
through the inlet line 75 and through passage 37 then discharged to the 
exhaust expansion assembly 23 through the passage 38 and discharge line 
56. 
With particular reference to FIG. 1, it should be noted that once the 
propulsion system of the present invention is installed within the boat, 
the system will be generally horizontally arranged at a slight downward 
angle from the engine toward the stern of the boat. The angle should be 
sufficient that the pump is oriented so as to receive water through the 
intake portion thereof generally designated at 80. The positioning and 
in-line relationship of the component parts creates greater stability of 
the boat than was possible with the conventional propeller drives, and 
also increases the maneuverability of the boat. 
As previously mentioned, the modified adapter and mounting plates of the 
present invention may be changed depending upon the make and model of 
engine which is to be converted to the horizontal drive disclosed. The 
embodiment discussed in the preferred embodiment disclosed an adapter and 
mounting plate specifically designed for an OMC engine. With reference to 
FIGS. 6-8 of the drawings, a modified adapter and mounting plate 22' 
specifically designed for a 50 horsepower MERCURY engine is disclosed in 
detail. 
The modified adapter and mounting plate 22' is disclosed as having an 
opening 27' through which the input shaft 29 of the gear box is centrally 
oriented. In order to provide clearance for the rectangularly shaped 
housing 28 of the gear box 24, an undercut portion 81 is shown as being 
made relative to the opening 27'. The undercut will allow the gear box to 
be securely anchored in position with the input shaft 29 extending 
upwardly through the central portion of opening 27'. The plate 22' also 
includes a plurality of openings 26 through which mounting bolts will be 
extended after appropriate gasket material is placed between the upper 
surface of the plate and the lower surface of the engine block. As with 
the adapter and mounting plate discussed above with respect to the 
previous embodiment, the plate 22' also provides a water cooling jacket or 
reservoir for the engine. In this regard, a water reservoir or recess area 
36' is provided within the upper face of the mounting plate so as to 
communicate with the water cooling system of the engine. To introduce 
cooling water to the engine, a fluid inlet channel 37' and an outlet 
channel 38' are provided intermediate the upper and lower surfaces of the 
plate so as to communicate with the recessed area 36'. An exhaust opening 
39' is also provided through the mounting plate and appropriate holes are 
provided on the lower surface of the plate so as to receive bolts 
extending through the flange 41 of the exhaust assembly 23. In a like 
manner, openings are also provided at the bottom of the plate for 
receiving bolts which extend through the flanges 31 on either side of the 
gear box housing. An additional series of openings is also provided which 
correspond to openings 67 in the plate 22 which openings are aligned with 
the openings 66 in the bracket assembly 25. 
As previously discussed, the power drive assembly of the present invention 
is designed to permit conventional outboard engines to be converted to 
horizontal drive engines which can be used with varying propulsion units 
or sources. In the preferred embodiment of the specification, the 
horizontal drive has been connected directly to a jet pump in order to 
obtain the benefits of increased safety and increased maneuverability 
within the environment of a water recreational vehicle or boat. Not only 
does the use of the jet pump offer greater drive flexibility in the system 
disclosed, but it also provides increased efficiency in steering and 
responsiveness to engine speed. It should be noted, however, that the 
propulsion system is not confined to use with recreational boats alone and 
that the system or assembly may be adapted for use with any type of boat 
having an outboard engine wherein the drive is to be converted to a 
horizontal orientation so as to enable the engine to power alternate types 
of propulsion or thrust producing units. 
In the use of the power drive assembly of the present invention, the power 
head is removed from the conventional vertical drive components, housing 
and propeller drive shaft of an outboard motor. Thereafter, the existing 
adapter plate is replaced with a modified adapter and mounting plate which 
is chosen so as to align with the exhaust and drive output of the engine 
and to provide aligned mounting holes by way which the adapter and 
mounting plate may be secured to the engine block through the bolt holes 
already provided therein. The adapter and mounting plate is secured 
utilizing proper gasketing materials and will provide support for the 
exhaust and gear box components of the power drive assembly. 
With the adapter and mounting plate partially installed, a gear box 
assembly having appropriate gear ratios is raised upwardly through the 
elongated openings 27 or 27' in one end of the adapter and mounting plate 
until the input drive shaft thereof is engaged in sealed and driven 
relationship with the output of the engine crankshaft. Thereafter, the 
gear box mounting bolts are inserted through the flanges on the side of 
the gear box housing and the housing secured to the adapter and mounting 
plate and engine block. 
Subsequently, the tuned exhaust expansion assembly 23 is raised into 
aligned position with the exhaust openings in the adapter and mounting 
plate and, using proper gasketing materials, the flange 41 of the exhaust 
system is secured into abutting relationship with the bottom of the 
adapter and mounting plate. Due to the offset nature of the muffler with 
respect to the mounting portion of the exhaust assembly, the muffler and 
tailpipe will be oriented generally in line with the drive train and 
offset with respect thereto. In order to provide coolant from the engine 
to the exhaust expansion assembly, the conduit 56 is connected to the 
fluid discharge opening 38 or 38' in the adapter and mounting plate and to 
the inlet 57 for the cooling jackets 53 and 54. 
The engine power head is subsequently mounted to the mounting base or 
bracket assembly 25 by bolting the adapter and mounting plate thereto. 
Thereafter, the propulsion unit 60 is secured to the brackets 70 and is 
thereby properly aligned with the output shaft of the gear box. A drive 
connection is made between the gear box and the input shaft of the jet 
pump or other propulsion unit thereby completing the drive assembly from 
the engine to the propulsion unit. With the components assembled, the 
water inlet line is connected through the openings in the side walls of 
the adapter and mounting plate so that during the operation of the engine, 
water may be pumped upwardly through the inlet line 75 through passage 37 
or 37' in the adapter and mounting plate into the engine and thereafter 
discharged to the expansion exhaust assembly. The engine and entire power 
drive assembly may now be readily installed within the boat as a unit with 
all the components thereof being supported by the base or frame 25. The 
base is thereafter secured to the hull of the boat with the tail pipe and 
thrust nozzle 82 of the propulsion unit extending through the transom or 
stern wall. Appropriate linkage connections L are thereafter made between 
the steering mechanism M and the propulsion nozzle 82 to thereby provide 
steering control for the boat.