Dual jet boat pump

A double suction, double volute pump for propelling a boat having each volute exhaust through a separate jet nozzle. The pump housing defines two intake passageways leading upward to either side of a double suction impeller. The housing further provides double volutes which receive water from each side of the double suction impeller and deliver it to dual nozzles thereby creating twin jets which may be employed to propel and control the boat. The double volutes each extend substantially full circle about the housing and terminate in elbows which lead to the nozzles. The nozzles are placed horizontally equidistant from the centerline of the impeller shaft and are controlled by steering linkages to operate in unison. Reversing control gates may be operated either together for reversing or independently for slow speed steering.

The present invention is directed to propulsion pumps for boats. More 
specifically, the present invention is directed to a dual jet boat pump. 
Pumps are employed in combination with power units for propelling boats in 
place of propellers and other conventional systems. These pumps generally 
suck water from underneath the boat and discharge it laterally in the form 
of a single jet. The resulting impulse drives the boat in the opposite 
direction. Generally, axial mixed flow pumps are employed in such boat 
applications. In these axial pumps, the impeller discharges directly into 
a central outlet having stator blades located therein and being shaped at 
the discharge end to form a single nozzle. 
A radial flow boat pump having double inlets and double volutes rather than 
a central axial mixed flow passageway has been developed which discharges 
through a single outlet jet. This pump is disclosed in a co-pending 
application entitled Jet Boat Pump, Ser. No. 382,374, filed July 25, 1973, 
now abandoned, assigned to the assignee of the present invention. The 
present invention constitutes an improvement on the boat pump disclosed in 
the above application, the disclosure of which is incorporated herein by 
reference. 
The present invention is directed to a double suction, double volute pump 
having dual jets which are directed laterally for jet propulsion of the 
boat. Water is drawn into the pump through scoops extending downwardly 
from the main portion of the pump housing. This incoming water is directed 
to both sides of a double suction impeller located centrally within the 
housing. The impeller then accelerates and distributes the water into two 
opposed volutes. Each of these volutes is wrapped substantially full 
circle about the impeller cavity. At the end of each volute, the water is 
directed through a nozzle laterally aft to form the propelling jets. This 
double volute and double nozzle configuration provides for hydraulic 
balance within the pump and a balanced casting. The balanced casting 
design simplifies the housing casting procedures and promotes a more 
uniform wall thickness in the casting. Further, the dual jet configuration 
provides simplified and balanced outlet paths. With a single jet, it is 
necessary that the nozzle be centered behind the boat. With the dual jet 
configuration, it is only preferable that the resulting impulse vector is 
centered behind the boat. Thus, the jets may be positioned at any 
convenient distance from the centerline of the boat. 
The extension of the volutes substantially full circle about the central 
impeller helps to increase the pump efficiency. The extended volutes 
gently reduce the velocity of the accelerated water exiting from the 
impeller. This creates a slow transition from a high kinetic energy level 
to a high pressure level. Further, twisting of the volute passageway to 
direct the water aft is delayed until the water has undergone the 
transition from high kinetic energy to high pressure. This is believed to 
help reduce the turbulence within the volutes resulting in an increase in 
efficiency and an improved jet. A further advantage of this dual jet 
system is that two smaller jets are employed rather, than a single larger 
jet. This reduces the effects of the water jet on a skier when the system 
is used for water sking. 
A steering and control system is employed using vertical vanes located 
within the nozzles for horizontal directional changes and control gates 
for reversing the flow to power the boat backwards. This system naturally 
gives a substantial amount of control which is further enhanced by 
independently operable reversing control gates that can be used like twin 
screws to turn the boat at low speed. 
Accordingly, it is an object of the present invention to provide an 
efficient jet boat pump employing dual jets. 
It is another object of the present invention to provide a jet boat pump 
wherein each of two volutes terminates in a separate nozzle thereby 
creating a dual jet boat pump. 
It is a further object of the present invention to provide a jet boat pump 
wherein a slow transition is provided for the water exiting from the 
impeller from high kinetic energy to high pressure in volutes extending 
substantially full circle about the impeller cavity. 
It is yet another object of the present invention to provide a jet boat 
pump having a substantial increase in low speed manuverability through the 
use of dual jets.

Turning specifically to the drawings, a pump housing, generally designated 
10, is illustrated as employing a single casting with a cylindrical insert 
to provide access to the center of the unit. The interior of the casting 
10 is best seen in FIGS. 2 and 3. Defined within the casting and insert 
are inlet passage means for drawing water into the pump, outlet passage 
means for discharging water from the pump and a cavity for the pump. The 
housing 10 generally takes on the shapes of the various passageways and 
cavities contained therein in order that the wall thickness of the casting 
and the resulting overall weight may be reduced. 
The housing 10 is split into two portions about a cylindrical parting 
surface 12 concentrically disposed relative to the shaft of the pump. The 
housing then is divided into a main housing 14 and a substantially 
cylindrical insert 16. The insert 16 is retained on the main housing 14 by 
bolts 18. With the insert positioned in the main housing 14, a pump cavity 
20 is defined centrally within the housing 10. Access to the pump cavity 
20 may be obtained through disassembly of the housing 10 by removing the 
substantially cylindrical insert 16. The breaking of the housing 10 along 
a cylindrical parting surface eliminates the difficulties associated with 
a horizontal parting surface. With a horizontal part, high pressure is 
developed within the pump cavity which tends to divide the two parts of 
the housing. Leaking is quite often the result. In the present housing 
structure, the substantially cylindrical insert 16 is primirily in 
association with the intake side of the pump which is maintained at a 
reduced pressure during operation. Only a small portion of the insert 16 
is subjected to high pressure in the pump. Thus, the possibility of 
leakage and pump failure is substantially reduced. 
The inlet passageway means are here defined as two intake passageways 22 
and 24 extending from below the pump upwardly about the pump cavity 20. In 
this way, water may be drawn from the body of water in which the boat is 
supported. Centered in the passageway 22 is a baffle 26 which helps 
stabilize the flow and prevents circular motion of the flow about the 
housing. A second baffle 28 is provided centrally in the upper portion of 
the inlet passageway 22. The inlet passageway extends in a circular path 
in either direction between baffles 26 and 28 to provide incoming water to 
the total inlet area of the pump cavity 20. A similar configuration is 
provided for the intake passageway 24 including baffles 30 and 32. The 
intake passageway 22 distributes incoming water to one side of the pump 
cavity 20 and inlet passageway 24 distributes incoming water to the other 
side of the pump cavity 20. 
The outlet passage means for directing water from the pump are defined in 
the present embodiment as two volutes 34 and 36 terminating in elbows 38 
and 40 which in turn lead to outlets from the pump. The two volutes 34 and 
36 defined by the housing 10 increase in cross-sectional area from the 
leading edges 42 and 44 to the ends thereof at elbows 38 and 40. This 
continuously increasing cross-sectional area associated with each volute 
34 and 36 allows for a slow transition between the kinetic energy 
developed in the water by the pump and the high pressure developed at the 
nozzle ends of the volutes. Starting at the leading edges 42 and 44, the 
two respective volutes 34 and 36 extend substantially full circle to the 
elbows 38 and 40. This extended volute design further enhances the slow 
transitional effect of the two volutes 34 and 36. The volutes also spiral 
about the housing substantially in a plane. This provides for a reduced 
overall length of the pump unit. The two volutes 34 and 36 are naturally 
formed about the central impeller cavity 20 in the direction in which the 
impeller rotates. This circumstantially results in a more compact design. 
The elbows 38 and 40 are also cast within the pump housing 10. The elbows 
38 and 40 redirect the water flowing through the volutes 34 and 36 
rearwardly in order that a propelling reaction impulse may be experienced. 
This directional change in the flow of water through the volutes is 
accomplished at a point where a substantial amount of the velocity of the 
water has been converted to pressure. This relatively late directional 
change is therefore accomplished with a minimum of energy losses. The 
elbows 38 and 40 are spaced equally from the center of the boat pump. When 
the horizontal components of the distances from the centerline of the pump 
to the resulting water jets are equal, the resulting impulse vector will 
be centered behind the boat. Thus, the boat will be driven by the jets in 
a straight line. The equal vertical placement of the nozzles helps provide 
a uniform trim. This centering of the impulse vector using two jets 
eliminates the need for a goose neck configuration necessary for centering 
the thrust from a single jet, boat pump. 
A pump shaft 46 extends centrally through the housing 10. The pump shaft 46 
is rotatably mounted in bearings at either end thereof. At the forward end 
of the pump housing 10, a bearing housing 48 is formed in the casting. A 
bearing assembly 50 is mounted on the pump shaft 46 within the bearing 
housing 48. The bearing is positioned between a shoulder 52 and a bearing 
cap 54. The inner race of the bearing assembly 50 is located relative to 
the pump shaft 46 by means of a first snap ring 56 located in a groove 58 
in the pump shaft 46. A second snap ring 60 is located in groove 62. A 
spacer 64 is positioned between the bearing assembly 50 and the second 
snap ring 60. Inwardly from the bearing assembly, packing material 66 is 
provided about the pump shaft 46. The packing material 66 is retained by a 
packing retainer ring 68 held in place by two studs 70. Access is obtained 
to the packing material 66 through holes 72 located in the casting. 
A bushing 74 is provided at the rearward end of the pump shaft 46. The 
bushing 74 is located in a cavity 76 formed in the housing. A spacer 78 
positions the bushing 74 in the cavity 76. An end cap 80 retains the 
entire bushing assembly. A seal 82 keeps water in passageway 24 from the 
bushing 74. Thus, the bearing assembly 50 and the bushing 74 constrain the 
pump shaft 46 to rotation about a fixed axis. To bring about such 
rotation, the pump shaft 46 extends forward from the bearing cap 54 to 
mate with the power plant. Splines 84 transfer the torque to the pump 
shaft 46. The housing is attached to the transom of the boat through studs 
86 and the bearing housing 48 extends through the transom along with the 
pump shaft 46. 
Means are provided for imparting energy to the water which is drawn into 
the pump. In the present embodiment, a double suction impeller 90 is 
employed for this function. The double suction impeller 90 is fixed to the 
pump shaft 46 within the pump cavity 20. The double suction impeller 90 is 
similar to that disclosed in the incorporated U.S. application, Ser. No. 
382,374. The impeller 90 includes shrouds 92 and 94, a central hub 96 and 
vanes 98. Holes 100 extend through the central hub 96 to help establish 
equal pressure on either side of the double suction impeller 90. The 
impeller 90 is constrained to a fixed position on the shaft 46 by means of 
snap rings 102 and 104 positioned in grooves 106 and 108 on the pump shaft 
46. The impeller 90 is constrained to rotate with the pump shaft 46. This 
may be accomplished by means of a key positioned in keyway 110. 
Two wear rings 112 and 114 are positioned within the housing 10 to provide 
a sealing means between the pressure side and the suction side of the 
impeller. The wear ring 112 is bolted directly to the main housing 14 by 
means of bolts 116. The wear ring 114 is similarly bolted to the housing 
insert 16 by means of bolts 118. The wear rings 112 and 114 have grooves 
set in helical paths on the surfaces in mating relationship with the 
impeller 90. The impeller 90 has similar grooves. These grooves help to 
keep the impeller 90 from freezing to the wear rings 112 and 114. 
Outlets are provided to finally control the jets of water as they exit from 
the pump to propel a boat. Pivotally mounted to the elbows 38 and 40 are 
control nozzles 120 and 122. The elbows 38 and 40 direct flow rearwardly 
to the control nozzles 120 and 122 which further direct the water from the 
pump. The elbows 38 and 40 are tapered to constrict the cross-sectional 
area of the passageways as the water flows rearwardly therefrom. This 
taper is best illustrated in FIGS. 5 and 7. It is believed that a taper of 
31/4 inches per foot is satisfactory. At the outer end of the elbows 38 
and 40, spherical surfaces 124 and 126 are provided. The spherical 
surfaces 124 and 126 mate with corresponding spherical surfaces 128 and 
130 located on the forward end of the control nozzles 120 and 122. Clevis 
lugs 132 and 134 are provided on each control nozzle 120 and 122. The 
clevis lugs 132 and 134 cooperate with pins 136 and 138 to pin the control 
nozzles 120 and 122 to the ends of the elbows 38 and 40. The pins 136 and 
138 are held in inserts 140 and 142 which are positioned in holes located 
through the elbows 38 and 40. Thus, each control nozzle 120 and 122 may be 
pivoted about a horizontal axis. This introduces the capability of trim 
control to the boat using the control nozzles 120 and 122. 
The control nozzles 120 and 122 each include a cylindrical bore 148 aligned 
with the tapered bore of the elbows 38 and 40. Extending from the circular 
bore 148 is a larger cylindrical cavity 150 which houses steering 
deflector vanes 152. The steering deflector vanes are mounted to pivot 
about a vertical axis extending through the centerline of the exhausting 
jet stream. Each deflector vane 152 is conveniently shaped as shown in 
FIG. 7 and is mounted on a short vertical pin 154 extending through the 
upper most portion of the respective control nozzle 120 and 122. A low 
friction insert 156 is provided about the pin 154. The deflector vane 152 
extends into a slot provided in the pin 154 and is held therein by means 
of a fixed pin 158. A second vertical pin 160 extends upwardly through the 
bottom of each respective control nozzle 120 and 122 to receive the bottom 
of each of the deflector vanes 152. The second vertical pin 160 is 
similarly attached to the deflector vane 152 by means of a fixed pin 162. 
A similar insert 164 is provided about the second vertical pin 160 in the 
control nozzle. Thus, mounted, the deflector vanes 152 may be pivoted 
about the vertical axis to effect directional control of the exhausting 
jets for steering of the boat. 
The deflector vanes 152 steer the boat in a right turn by rotating 
counterclockwise as seen from above. The water on the right side of the 
jet is deflected toward the right. The water on the left side of the jet 
is naturally drawn along the surface of the deflector vane 152 and thereby 
also is deflected toward the right. A portion of each vane 152 extends 
upstream of the pivot axis defined by pins 154 and 160. In this way, the 
upstream portion of each deflector vane 152 will tend to cut off the side 
of the jet toward the outside of the turn. 
Steering control of the deflector vanes 152 is accomplished through a 
steering control rod 166 which is pivotally connected to a lever arm 168. 
The lever arm 168 is fixed at a distance from the steering control rod 166 
to the second vertical pin 160 on the left hand control nozzle 122. Fore 
and aft motion of the control rod 166 results in rotational motion of the 
second vertical pin 160 which effects steering through the steering 
deflector vane 152 in the left hand control nozzle 122. Also attached to 
the left hand vertical pin 160 is a second lever arm assembly 170. A 
similar lever arm assembly 170 is included on the right hand vertical pin 
160. A tie rod 172 extends between the left and right hand lever arm 
assemblies 170. The tie rod 172 is pivotally mounted to each of the lever 
arm assemblies 170 and rotational motion of the left hand vertical pin 160 
will result in similar rotational motion of the right hand vertical pin 
160 which in turn causes the right hand steering deflector vane 152 to 
track the motion of the left hand steering deflector vane 152. Thus, both 
jets are deflected in an identical manner for control of the boat. 
Attached to the control nozzles 120 and 122 are reversing control gates 174 
and 176. The reversing control gates 174 and 176 operate in a 
substantially identical manner to the reversing control gates illustrated 
in the incorporated co-pending U.S. application, Ser. No. 382,374. A 
substantial advantage of the dual jet configuration disclosed in the 
present embodiment employs the reversing control gates 174 and 176. 
Specifically, during low speed manuvering, the reversing control gates 174 
and 176 may be independently operated to effect a steering capability 
similar to that available with twin screw boats. This effect is brought 
about by lowering the appropriate reversing control gate down over the 
nozzle 120 and 122. The other control gate is retained above the opposite 
control nozzle. When power is provided to the pump, one jet will continue 
aft while the opposite jet is directed forward. The resulting is a couple 
which will bring about rotational motion of the boat without substantial 
fore or aft motion. 
Thus, an efficient boat pump is provided which incorporates the dual jet 
configuration for added versatility and efficiency. While embodiments and 
applications of this invention have been shown and described, it would be 
apparent to those skilled in the art that many more modifications are 
possible without departing from the inventive concepts herein described. 
The invention, therefore, is not to be restricted except by the spirit of 
the appended claims.