Thread: '02 Yamaha C90 Power Tilt/Trim Creep Help!

Could be the orings on piston or it could be the valve, or even the manual valve leaking. It could also just be dirt in the fluid causing the leak.

Originally Posted by Lund

Please help. My '02 Yamaha C90 is slowly creeping down. Power tilt and trim work fine, I checked and looks like plenty of fluid up to the reservoir screw and no noticeable leaks. It is my first boat for 2 years now and I have never had this issue before. I tilt the engine up off the ground about 4-6 inches and it is on the ground within an hour. I have double-checked the manual tilt screw and it is tight. I am trying to scour the internet to find out what to do and getting nowhere. Something said something about checking a check valve but can't find it/I don't know where that is on the parts diagram (below).

For convenience here is the parts diagram (not an endorsement for the website)
POWER TRIM TILT ASSY - 2002 Outboard 90hp 90TLRA | Crowley Marine

Any and all help would be greatly appreciated.

I’m just a shade tree mechanic, but if it were me, I might try trimming it all the way up, then cracking loose the manual valve/screw a few times, beware of course, it will drop fast when you open that valve. Watch fingers! But it might flush something out or unstick something. And its free.


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I'm with MD, I'd bet its the o-rings around the trim piston (#64) or the tilt piston (#20) are worn and allowing the fluid to seep past. If you're mechanically inclined its not hard to replace them (Basic Hydraulics). The issue is you'll need the correct spanner wrenches to remove the caps for disassembly. I'd bet there's several videos on u tube that will show you how to do it.
If all else fails, there's companies that offer reman services where you send the complete assy in and they rebuild it for you. Do a google search to see if that's something you may be interested in.

Chris

I agree with Chris. I am a hydraulic systems guy and if you do not have visible leaks, you have what is called an internal bypassing leak. Fluid is leaking around the piston back to the other side of the piston to the rod side. Some of the fluid is going back into the reservoir, and the other fluid is bypassing around or through torn o-rings or seals coming to the rod side, letting the piston down there for putting your motor down on the ground. You need to replace the seals that and circle the piston. You could have some O-rings leaking in the hydraulic valve but usually it’s a seal on the piston is the problem. The control valves for trim and tilt are what they called normally closed center or all ports blocked valves therefore, fluid leaking around them is usually not issue.


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UPDATE:
So, after further research and calling two different marine mechanics, I decided to just let the shop do it. The mechanic said it more than likely is the O-rings (the motor being 22 years old runs great though) exactly like MDCrappie, NCkenner, and BabyFinster stated. The shop quoted me about $200 and after buying the two pin wrenches ($60 each!), hydraulic fluid, and the O-rings figured I’d just let him do it. I would have tried it myself if the pin wrenches were not so much money for my one-time use. Thank you all for your help!! I dropped it off Thursday last week and the mechanic said the O-rings should be in by Friday. Here is to hoping it is ready by next weekend! It’s okay though, it’s been so incredibly hot here in Alabama.

A friend gave me a boat 4 years ago that had sat for 7 years unused. It has a 1998 90hp Honda engine. Got it running after soaking cylinders with marvel mystery oil overnight. Trim and tilt worked at first but started leaking down and using fluid. I did not have the tools or experience to rebuild the unit. I sent the TnT unit to Five stars marine in Port Richie Florida for a rebuild. It took some effort to get the TnT off the Honda. I used UPS to mail it to them and they rebuilt it. They hot tanked it. Polished rams and seats, installed new seals and o-rings, charged a little more to replace the "ram caps"..motor was still working so they did not have to replace it.. I did not have them paint the unit. I painted it when I got it back. So far no problems..It was not cheap, think it ended up over $400

Originally Posted by RobertFL

A friend gave me a boat 4 years ago that had sat for 7 years unused. It has a 1998 90hp Honda engine. Got it running after soaking cylinders with marvel mystery oil overnight. Trim and tilt worked at first but started leaking down and using fluid. I did not have the tools or experience to rebuild the unit. I sent the TnT unit to Five stars marine in Port Richie Florida for a rebuild. It took some effort to get the TnT off the Honda. I used UPS to mail it to them and they rebuilt it. They hot tanked it. Polished rams and seats, installed new seals and o-rings, charged a little more to replace the "ram caps"..motor was still working so they did not have to replace it.. I did not have them paint the unit. I painted it when I got it back. So far no problems..It was not cheap, think it ended up over $400

B.O.A.T. = Break out another thousand!

Oh I spent thousands on the boat before I was done.... batteries, Garmin fish finder. 80 thrust trolling motor, seats. Rod holders, I put off white truck bed liner on the floor. Etc....in the end it was worth it, I have had a few boats in the past so I know about the thousands.