tilt trim oil

I have a 1985 force 125 hp iam replacing the tilt trim motor what kind of fluid
should i use

Re: tilt trim oil

Transmission fluid or 30w motor oil, whichever resembles the current fluid.

Re: tilt trim oil

The ideal thing is ISO32 hydraulic oil. The pump reverses direction with slider valve and it won't move until backpressure drops. Motor oil can sometimes be too thick. If you keep running pump after fully tilted then pressure spikes to max. A system that is in really good condition can take 5-10 mintues before the back pressure drops with motor oil. Hydraulic oil is thinner and the pressure equalizes much more quickly. Additionally motor oil can hold suspended air bubbles and be troublesome when refilling a dry system. If the choice is in front of you then avoid ATF. ATF is cheaper than hydr. oil and it eliminates air bubble problems when building new systems but ... systems with oil seem to last longer. Almost all of the systems I get sent for rebuilding that are less than 15 years old have ATF in them. There is something abut ATF that causes the orings to split with age instead of just hardening and getting flat spots.

Re: tilt trim oil

Thanks for the info also what is the procedure to purge the system should
it be tilted up or left down?

Re: tilt trim oil

raise it fully and block into place. disconnect two front oil tubes from pump. run system "up" and all the oil in resevoir will come shooting out of ports. Put some paint thinner into resevoir to dissolve residue and run pump to dry. do not over-run because you are also dissolving lubrication. Just run until fluid stops. leave filler plug out and let it drip for a while. remove blocking and let weight of engine force oil out of tubes.

If changing from ATF to oil then you may want to remove additional parts and give it a more thorough flushing.

Hook everything back up and refill with oil. leave out filler plug so that air can enter or exit resevoir. Run sytem up/down a few times. it is self bleeding. you will probably need to top it off once as cylinders fill back up with oil. You'll know when resevoir is getting empty because system will stop going up. It takes about a pint.

Re: tilt trim oil

RRitt thanks for the help but what if the motor is already down should i try to lift it up or just put the motor on and fill the resevoir and cycle it till it is full

Re: tilt trim oil

ph98223 said:

RRitt thanks for the help but what if the motor is already down should i try to lift it up or just put the motor on and fill the resevoir and cycle it till it is full

Click to expand...

that depends whether or not you want to flush the system. The hydraulic cylinders have fluid both above and below the piston which makes them bidirectional. if you use new pump to raise system then your old fluids from trim cylinder will end up in your new pump.

the last 3/8" of trim piston doesn't make any contact with seals. There is probably 1/8" sticking out and you might be able to grab it with vice grips and pull out the piston. try not to scratch it because it can hang on the retaining slug in the future. when finished use a fine file to smooth out the score marks. Don't go past the very end of piston because then you might end up with scratches where you need a good seal.

If your system doesn't have any water, dirt, or rust in it then there might not be any good reason to flush it.