The Bay Company
Marine Sales & Service
(907) 874-3340 Wrangell, Alaska
(907) 826-3341 Craig, Alaska
431 Front Street
P.O. Box 797
Wrangell, Alaska 99929
Phone: (907) 874-3340
Fax: (907) 874-2592
1250 Hill Top Drive
P.O. Box 648
Craig, Alaska 99921
Phone: (907) 826-3341
Fax: (907) 826-2592
For over 50 years, Outboard Jets has provided quality conversion units for
outboard motors designed to allow a boat to be used in locations where a
propeller driven boat is unable to operate – in shallow, ankle deep water.
1. Which one fits my motor?
You must know the motor make, year, HP, long or short shaft, remote or tiller steering, number of cylinders and whether it’s
through hub exhaust or not.
2. What speed will I get?
It depends on the boat and the weight. A good setup will get about 80% of propeller speeds when using mid range prop pitch. A
light weight prop boat using a high pitch prop can run twice our outboardjet speed.
3. Can we change jet impeller pitch for load or speed?
No. Unlike a propeller drive, a jet can develop full HP at a standstill. We choose an impeller that gives rated factory RPM at full
throttle. RPM hardly varies between a heavy load and running fast with a light load.
4. What is the clearance between impeller and liner?
The clearance is approximately 1/32 of an inch (.03125). There is some off center between impeller and liner due to
manufacturing tolerances so check at the closest point. Less than 1/32 of an inch is ok if the impeller does not rub. More
clearance than 1/32 of an inch will drop pressure and performance.
5. Can you use any other grease besides Lubriplate 630 AA and why do you recommend against using a lever type grease
Any grease of the same consistency (NLGI 1) which is water resistant should do the job. The main thing is to keep grease in the
bearing cavity and water out. We prefer a hand held jiffy lube since it does not create high pressure. If a cartridge type lever gun
is used, it should be pumped gently! Excessive pressure will invert the rubber seal lips and seals will no longer keep water out.
6. Why don’t we make jet drives for less than 25 HP?
We lose about 30% of the HP when converting from propeller to jet drive. With less than 25 HP, it is difficult to plane a boat with
two people. If it won’t plane, it will not operate successfully in shallow water.
7. What can cause RPM to be too low or too high?
Load has nothing to do with RPM on a jet drive (see question number 4, 11). Impeller pitch and diameter is based on sea level
operation. At higher elevation, you will lose RPM and may have to drop down one impeller size. Long use in corrosive
conditions may create pin holes in the exhaust tube which builds up back pressure and reduces RPM. Excessive RPM is
usually caused by air entering the pump. It can be caused also, during start up, if the leading edges of the blades are blunted
from gravel. A rough boat bottom, keels or damage ahead of the intake can introduce air, as well as setting the motor too high.
8. How much gouging can a liner have before it needs to be replaced?
Gouging from gravel is normal. There is considerable surface on the liner to provide pressure sealing. If it is worn such that all
the shim washers are on top of the impeller, and blade clearance is still more that 1/32 inch, the liner and/or impeller need to be
replaced. If you do replace the liner because of gouging, check performance before and after replacement to see how much, if
any, loss the gouging caused.