1989 125hp Force Trim Dropping and Lower Unit Leaking

[LakeTexomaBoater]

Hello all, I posted before about this engine and finally got the book on it. Im having a problem though, I tried to check to make sure the manual release valve for the trim was tight.. the book says its located on the bracket, yet I see no valve, plug, anything that appears to be "turnable". I do however see a knob on the side of the main trim cylinder, but it turns both ways and never tightens. Its not leaking around there at all, but when I turn it, fluid does pour out.

Another problem, located under my lower unit, there are two bolts that are perfectly vertical. On each side of those two bolts are two small holes, oil is dripping out of those two holes, would that be from a bad oil sealer or any ideas?

Oh, and one more thing.. When I have the motor raised up, it seems that each time I take it out, with that angle, fuel has leaked out and has pooled in the covers in front of the carbs. I know that can't be good. Any ideas there?

I know, lots of questions, I did buy a book, but the troubleshooting in that book really does not answer anything I need.

Thanks in advance.

 

[Dave K.]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

my guess is unburned fuel leeking from the weep holes (common) and the fact that some fuel is coming back out the front of the carbs when the motor is tilted. again pretty common. there are some posters here that will know for sure but i don't think it's anything to worry about. btw - those two bolts you mention are the fill & vent screws for the l/u oil & their will be a darin screw (smaller) underneath the cavitation plate.. be sure to buy NEW washers for all the screws each time you change out the oil.

 

[LakeTexomaBoater]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

ok, good on the fuel part, but the two bolts under it aren't screws. The fill and vent screws are on the bottom stern side of the motor, those are marked, these two are literally under the stern side of the unit.

 

[RRitt]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

Okay - I can't help you with anything but trim. Hopefully someone else can help you with the other questions regarding lower unit and leaking carbs.

Your trim system has three main parts and a small handfull of support components.

12V reversible hydraulic pump
*********************
On the side of your transom clamp is a 900-1200PSI hydraulic pump. The 12V electric motor is assembled onto a base which doubles as the fluid reservoir. The electric motor will last for 100 years or until water gets inside (whichever comes first). Don't loosen the two top screws on motor (EVER). If you do then your seals are compromised and your motor will soon die.

On the side of the reservoir is a thumbscrew with 3/8-24 threads. It does not need to do anything except keep water from getting into reservoir. The reservoir should be topped off with 30W motor oil (non detergent). On this particular system it doesn't make any difference if the system is topped off in the raised or lowered position.

Underneath the reservoir is the actual fluid pump (aka valve body). Generally speaking these pumps only have two problems. The first problem is bleed down. When your engine bleeds down it is almost always the valve body that needs to be fixed. Rebuilding a valve body is meticulous work with a 50% success rate amoung competent DIYers. The second problem is stripped threads while servicing the electric motor. The valve body is made from aluminum and the brake lines are stainless steel. A lot of mechanics try to pull the fluid lines into place using the threads. It doesn't work very well and the threads get stripped. I see a LOT of this.


Trim cylinder
*********************
underneath the engine there is an odd looking piece that goes between your transom clamps. It has a shock absorber looking thing on each side and a five sided post thing in the middle. That five sided post thing is your trim piston. It pushes the engine up while the prop is spinning. Just about the time that your prop comes out of the water your trim piston should reach the end of it's stroke. These rarely break but when they do it is often spectacular. A loud pop, spewing fluid, gearcase dragging on roadway, etc etc. Don't use ATF and don't tow your boat without a trailering bracket. The only other concern with this part is galvanic corrosion. The large shaft that holds this part in place is made from stainless steel. Put it in saltwater and the trim assembly is punished badly. Very often the corrosion gets underneath the piston centering ring and pushes it out. Once the centering ring gets pushed out of trim cover then the whole assembly is pretty much toast. If you use ATF them the piston ring often splits under pressure after about 15 years. It is fairly easy to fix in freshwater boats. Just make sure to treat the cover like an cylinder head and use uniform torques.

Tilt cylinder
*********************
On the left is a shock absorber. On the right is a tilt ram. The shock dampens the system and helps to smooth out surges in pressure. The tilt cylinder lifts the engine for trailering. Like the trim cylinder these rarely break in freshwater. Examine the seal where piston shaft comes in and out of cylinder body. There is a hard plastic fitting that scrapes away water and debris. If it is beginning to crack then your tilt ram should be rebuilt. Once water gets inside it might ruin the piston. Seals are cheap. Pistons are not. A common problem amoung saltwater boats is corrosion around tube fitting and band collar. The fitting can be bought from NAPA as a weatherhead 1441. The band collar is S.O.L. Fortunately this is a low pressure fitting. You may be able to fabricate a new collar or repair your old one with stainless sheet metal from local hardware store.

Support items
*********************
Underneath the swivel bracket is a stainless steel bracket where the trim piston strikes. You need this bracket because it bears the brunt of your horsepower.

The entire assembly is held in place with two mounting shafts. The lower shaft is 5/8" dia and about 12" long. The upper shaft is 9/16" dia and about 9" long. If the threads on either shaft get damaged then just drill out for cotter pin. If you replace the lower shaft then aluminum might be better in saltwater (70-100HP). The upper shaft should be stainless. 9/16" aluminum might bend.

The pump is connected to the valve body with four stainless steel tubes. The tubes are standard SAE brake tubes except that they are made from non maleable stainless. The tubes commonly fuse into the aluminum components when exposed to saltwater. Great care should be taken to avoid ruining the aluminum. The two upper tubes go to the two rear ports on pump. These are low pressure "down" tubes and may be replaced with aluminum, stainless, or CuNi. The two lower tubes go to the two front ports. The trim tube goes to downward facing port and the tilt tube goes to front side port. The second side port is not used. These tubes are high pressure "up" tubes and may only be replaced with stainless or CuNi (aluminum/copper will explode and steel will rust).


and i think that's it. i don't understand what you were asking, but i'm sure the answer is in there somewhere.

 

[LakeTexomaBoater]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

Thanks for all that information, but what I am asking is where exactly is that manual release valve for the trim, so I can make sure that is tight. And where is the thing to fill it with fluid. "The reservoir should be topped off with 30W motor oil (non detergent)"

 

[RRitt]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

The manual relief valves are either installed or not installed. There is no adjustment on prestolite valve bodies.

Oil is added by taking out the filler plug and squirting it into the hole.

 

[LakeTexomaBoater]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

So that is the thumbscrew with 3/8-24 threads on the side of the reservoir?

 

[LakeTexomaBoater]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

Im guessing yes?

 

[RRitt]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

part #14

http://www.mercruiserparts.com/Show...&bdesc=TILT+CYLINDER+&+MOTOR+&+PUMP+(DESIGN+I)

 

[LakeTexomaBoater]

Re: 1989 125hp Force Trim Dropping and Lower Unit Leaking

Excellent, Thank you for that picture. It helped a ton. That is the place I thought it was.