Hey all knowing TFFers,

I have an 89 Mercury XR4 150 hp. . . The tilt & trim is still working properly HOWEVER, when I trim it all the way up. . .it can't keep it up. It begins a slow decent all the way back down. It takes 10-15 minutes to fall down. . .I checked the fluid but that wasn't the case (it was full).
Any ideas? Anyone. . . .

Thanks,

Longhorn

just lock it in place when it gets up

Probably a leaking hydraulic cylinder.

The Hydraulic cylinder has a internal leak. Don't know if it is worth the expense to have it fixed at this point as long as it is working when you are running the boat. When it quites altogether is the time to fix it.

how much to fix?

Do it your self, about twelve cents for an o-ring. Repair shop $125 plus. That was what it cost me to do my trim and tilt.

Where did you get the o-ring from? Mine has a leak, and would be very interested in where you found your o-ring.

My motor is a fifty horse Force made by Mercury. I went to a Merc dealer and they sold only a complete cylinder. I bought the o-ring at Tractor Supply. In the tractor parts they have a whole board of o-rings and you just have to find the right size. Also a guy could take the old o-ring to a hydraulic repair shop or gasket supply company and have it matched up.
Another option is to take the cylinder off and take it to a hydraulic repair shop. They could probably repair it for you at a resonable price. If I could have found a repair shop when I needed it, I would have let them do the repair just because they have all the spanners to disassemble the cylinder. A tractor repair shop might be a good option also.

Thanks

If leaks down and stops at the trim rams and stops then it the port trim ram and needs to be replaced bad check valve OPTI

I was going to suggest the check valve. If the ram was leaking, you would see fluid on the shaft.

An external oil leak will show on the shaft. In my case, the piston o-ring was worn and hard and was letting fluid leak past INTERNAL. I could trim out and in a few minutes it would leak down and drop the front of the boat down. On land, I trimmed the motor out, then climbed on the lower unit and it slowly lowered. I rebuilt the cylinder and have had no problems since. A check valve bad is possible, but I would lean towards the cylinder based on his description.

Can a normal boat shop mechanic fix this tilt & trim issue or to I have to find a "specialist" with hydralic stuff?

A good boat shop should be able to fix. I would ask if they will repair or replace though.