OVERHAUL OF JET DRIVE
All numbers given in this guide are off of the Berkeley 12JG Schematic
is essential you are familiar with sections I and II of this manual.
Proper trouble shooting will help you determine which parts must be
removed from your jet drive, or the boat, in order to perform the
necessary repairs or parts replacement. Starting at the back of jet,
outside the boat, all the parts for steering, reversing, and trim
control are accessible. Next you have the bowl and impeller assembly
and wear ring and finally the suction piece, shaft and thrust bearing
assembly and front packing gland assembly. With careful thought, you
can do everything except replace the thrust bearing without taking the
entire jet drive out of the boat. Only in rare instances should engine
removal ever be necessary.
Disassembly (re-assembly of the steering and reversing mechanism)
this assembly, all the parts are external and no seal between the jet
drive and hull needs to be broken, unless you are replacing cable
packing glands, items #18, #15 and #16). See the transom housing parts
illustration (#27). Normally repairs in this area will center around
replacement of gasket (#17) and the 4 bushing (#29) on the lower pivot
shaft, open steering shaft and the two reverse gate shafts.
the pins, (#55, #15 and #16 - 2 ea.) in order to separate the reverse
gate from the steering nozzle and the steering nozzle (#6) from the
nozzle housing (#5). Remove the 5/16" x 1" socket head cap screw (#42) from the left and right reverse gate pivot shafts. Push
the pivot shafts into the steering nozzle until the reverse gate is
free. Use of a solvent such as liquid wrench, WD-40 and a drift and
hammer may be required where units have been in service a long time,
especially in slat or brackish water. Lift off the reverse gate, inspect and set aside for replacement, repainting or reinstallation. Remove 2 nylon bushing (#29) and inspect. Either replace or save if no wear damage is apparent.
Remove 5/16" x 1" socket head cap screw (#42) from lower steering pivot shaft. Push
shaft up into nozzle area. Be cautious the pin does not fall into the
bowl and cause loss of time fishing it out. It is stainless steel so a
magnet does not work.
Remove the tiller shaft set screw (5/16" x 3/4" #43) using a 5/16" open end wrench. Note this set screw has a nylon lock button. The screws should always be replaced when it has been removed. Remove
upper woodruff key (#36) after removing tiller arm and push or tap the
tiller shaft (#15) down through the nozzle housing. Inspect the nylon bushing (#29) and discard if worn. Inspect
the woodruff keys (2 ea.) in the tiller shaft and the keyways in the
nozzle (#6) and steering housing (#5). If the key way is worn your
steering will be loose and steering failure is very possible. Replace
either or both of items #5 & #6 if they are worn. Inspect the
O-ring (#20) on the steering nozzle and replace if damaged. A bad
O-ring causes thrust loss around the nozzle (especially in turns) and
excess water spray.
Use a 1/2" box end wrench or
socket and ratchet to remove the 8 - 5/16" x 3/4" cap screws (#51) which
secure the nozzle housing to the after bowl face. Remove the nozzle
housing and set aside the gasket (#17) for replacement.
is reversal of steps 1 through 4. Make sure all parts are serviceable,
all threads are clean. Use a light grease such as Lubriplate on all
moving parts to assure easy assembly and free movement..
Check reverse gate and steering operation after re-assembly to insure
full port to starboard steering and a full open reverse gate in the
forward control position.
Bowl and Bowl Bearing
introduction of fresh oil through the oil reserve plugs (#48), removal
of the bowl is only required if you suspect foreign object in the bowl
vanes, loose bowl bearings, or you must remove the impeller.
1. Remove the transom housing (#1) by disconnecting the reverse gate
cable, steering cable and transom housing retaining bolts. The housing
is sealed using gasket (#6) and O-ring (#7). Most builders also are
liberal with G.E. Silicone Sealant, so use of a large screwdriver, a
wide stiff putty knife or rolling head pry bar may be necessary to break
the transom housing loose from the boat transom and jet drive bowl.
cable lengths permit, the housing may be slid aft and off the bowl. If
the lengths do not permit, the cable seals must be loosened so the
cables can be removed from the transom housing.
2. Remove the bowl by removing the 8 bowl to suction piece cap screws (#4) with a 3/4" box end wrench.
Separate bowl from suction piece and slide aft, off the impeller shaft.
Inspect bowl for damage to the bowl vanes, debris in the vanes, worn bowl bearings (#26) or bad seal (#28).
Bowl Bearing Replacement
Remove the end cap (#11) with a 15/16" box end wrench.
the bearings forward into the bowl using a bearing removal tool or any
suitable drift which passes the bowl end cap threads and has a shoulder
to seat on the bowl bearing.
Drive first bearing (#26) into bore from the front side until the bearing face is flush with the bore shoulder.
Drive rear bearing (#26) into bowl from the back side until bearing face is flush with bore shoulder.
Install bowl bearing end cap (#11) using Loctite (brown).
lip seal in bowl counter bore with the lip facing forward. This seal
does not keep oil in; it keeps debris and high pressure water out of
the bowl bearing.
Note: Worn bowl vanes may be renewed by filing
the dings and blunt edges off until there is a fine edge facing the
water. The bowl vanes should be dressed so all the edges are the same
distance from the front of the bowl.
Impeller and Wear Ring
the impeller nut (#32) using a 1-13/16" box end wrench or a 1-13/16"
socket which has been modified so it will slip over the impeller shaft
and has a holding handle welded on.
The impeller nut is a right hand thread and turns counter clockwise for removal
In cases where the impeller nut is frozen to the shaft due to
extensive immersion in salty or chemically tainted water, it may be
necessary to use a penetrating oil, apply heat, or even use a torch to
cut the nut. Since the impeller shaft is stainless steel, careful
application of a cutting torch will not damage the shaft or shaft
threads. Use caution!
The impeller has a cast in groove on the
hub. Use a puller with three or four inside jaws to grip the hub
indent. Tighten the jacking screws and give it a blow with a ball peen
hammer. It may be necessary to repeat this procedure several times
before the impeller breaks loose. Liberal use of a penetrating oil may
Note: The impeller fits on a straight shaft section
with a long keyway. There is a shoulder on the shaft which the front
of the impeller hub rests against when the impeller is fully seated.
the impeller for broken blade, cracks or excess wear on the wear ring
seal area and dinged or chipped leading edges on the impeller blades.
a. The wear ring area may be dressed if there are grooves worn in it and a new wear ring sized to fit the smaller diameter.
Small nicks and dings or sand worn impeller blade leading edges may be
renewed using a small die grinder, hand files and crocus cloth.
proper blade shape is similar to an airfoil with the flat side on the
top of the blade and the curved shape on the underneath side of the
blade when you look at the impeller from the front. The edge should not
be knife sharp, but finished to about a 1/32nd radius. Try to keep
the leading edges of the blades all the same length.
wear ring & insulator (#13 & #14) from the suction piece by
prying the parts out. This is facilitated with a small rolling head pry
bar. You will remove the wear ring and the plastic liner.
a. Discard the wear ring and insulator if worn.
Install a new wear ring and insulator in standard or undersized fit,
according to the impeller eye size of your impeller. The wear ring
should have rotating clearance only, when the impeller is installed.
c. Check final fit by slipping the impeller into the installed wear ring and rotating the impeller.
d. Re-check fit after the bowl is installed.
Reinstall the impeller in reverse order.
Use brown Loctite or Neverseize on the shaft and key, then slide the
impeller onto the shaft with the key started into the keyway.
b. Use a tube type driver which fits over the impeller hub and seat the impeller tight against the shaft shoulder.
c. Install the impeller nut and tighten it to about 75 foot pounds or until the impeller is seated against the shaft shoulder.
If you drive the impeller onto the shaft with excess force and the
front of the shaft is not supported, your hammer blows will be
transferred to the thrust bearing and small flats will be made on the
ball bearing along with dents in the bearing races. Result: premature
thrust bearing failure. The impeller should be a hand to light press
fit on the shaft.
d. Shaft and bearing assembly repairs or
replacement are possible once you have removed the impeller and the
suction piece out of the boat, or the engine has been removed.
1. Removal of the entire jet drive or suction piece assembly only are preferable to pulling the engine.
the suction piece assembly/pump assembly by removing the bolts and lock
washers (#5 & #6), which secures the suction piece to the intake
housing which is fastened to the hull.
Pry up on the suction piece to break the gasket seal between the suction piece and the intake housing.
the suction piece aft, out the access hole in your boat transom. The
splined shaft will slip out of the U-joint which is fastened to the
Note: 4 point engine mounts require no support for the
engine. If you have a 3 point mount which rests on the suction piece
housing, a suitable lift must be provided for the rear of the engine so
the bell housing can be unclamped from the suction piece. It is
advisable to install a wooden block between the hull and the engine bell
housing to safely support the engine while the jet drive is removed.
Remove the bearing cap cap screw (#49 - 4 each) from the bearing
housing and tap the bearing housing to remove it from the suction piece.
3. Remove the shaft and bearing assembly from the suction
piece using a protective wood block or soft mallet and drive the shaft
forward using a heavy hammer.
4. Remove the Tru Arc snap ring (#31) from the shaft.
Press the bearing from the shaft using a press or suitable mechanical
bearing removal/installation tool. Support the bearing on the inner
race wile pulling it from the shaft if you plan to reuse it.
Inspect the shaft, especially the bowl bearing end and straightness in
the splined through bearing fit areas. Repair or replace as indicated.
Undersized bowl bearings are not available as factory replacement
parts, so the shaft must be sized to original specification. Use the
undamaged forward area to obtain shaft diameter measurements.
Suction piece packing rings are removed easily once the shaft is removed.
Remove packing gland nuts (#39) and remove the split packing gland.
Pry out old packing rings (#23, set of 5) and slip new packing rings into place.
Remove the packing rings in a similar manner if the shaft is in place.
Use a packing puller, or make one with a long self tapping sheet metal
screw. The packing rings are split for installation over the shaft.
Make sure to stagger the split in the rings 90 degree intervals.
Reinstall the shaft and bearing assembly in the suction piece after installing the bearing on the shaft.
bearing so the thrust side (no groove for bearing balls) or side marked
for inner race thrust is toward the shoulder on the impeller shaft.
The thrust goes from the shaft shoulder to the inner bearing race and
through the bearing balls to the front face of the outer race. The
bearing housing cap (#8) absorbs the impeller thrust and clamps the
outer race so it cannot spin or move fore and aft. Slide the shaft
and bearing into the suction piece and slide the bearing home by
pressing or driving on the outer race only. Driving on the shaft will
damage the thrust bearing resulting in premature bearing failure. Tighten
the packing gland lightly, just until there is slight drag on the
impeller shaft. Final adjustment should be made with the shaft turning
and the pump shaft submerged. Reinstall the suction piece with shaft
bearing and impeller/wear ring in the boat using a new gasket (#3).
Installation of the suction piece assembly rather than the entire jet
drive makes positioning the unit and shaft insertion into the splined
Note: You may prefer to fully assemble the jet
drive before installation. In this case, help form a second person or
suspending the drive from the overhead may expedite getting the shaft
splines into the U-joint and the suction piece aligned without gasket
Note: You may find it helpful to use heavy grease or a gasket compound to help hold the gasket in place on the intake housing.
all components in the reverse order to their disassembly, making sure
all seals between the boat and the jet drive are intact so there will be
no leaks when you water test your boat.
All models of Berkeley jet drives are similar so only minor variations in assembly/disassembly are required.
especially careful of the rubber accordion boots used underwater on
some models. A small puncture or tear will result in a flooded boat. Berkeley
"E" or insert model jet drives do not have an intake housing. The
suction piece is bonded to the hull. Removal of the shaft and bearing
assembly requires removal of the engine.