Mercruiser trim problem

[727_pilot]

I just rebuilt one of the power trim lifters, one was leaking when I bought the boat. Some water had gotten in the oil besause it was milky. I have bled the system, and now the outdrive will go up, but not down again. The pump is running and it is full of oil.<br /><br />Any suggestions?

 

[moderator1]

Re: Mercruiser trim problem

Moving to I/O questions.

 

[denniz]

Re: Mercruiser trim problem

Will it go down if you stand on the drive and tilt down? If not pull the rear bolt(hinge pin) [above the prop] have someone hit the down button. could be just one cylinder(lines crossed)??

 

[walleyehed]

Re: Mercruiser trim problem

Seven two, I've got an idea, but you most likely don't want an IA's view on this......<br /> If your hoses are correct, you have a hell of an airlock which will require loosening the hydr. fitting at the fwd portion of cyl. Just crack it enough to hear air, or see fluid.<br />If you can get it down (by cracking fittings and applying weight to unit) you can pull nuts from thru-bolt at rear and remove that end of the cylinders....careful with the rubber bushings.<br />With unit fully retracted, refill res. and run trim out slightly while someone watches cylinders. If they both move, go all the way out, and hit the down button....if they go down, continue the cycle 5 or 6 times and this will usually work the air into the res. If They DON'T go down with trim motor, you will have to crack fittings and bleed down again at which point I would say you have trash in a check valve....<br />Good luck!

 

[727_pilot]

Re: Mercruiser trim problem

Thanks guys, and I'll take an IA's advice any day.<br /><br />It will go down if someone stands on it, so there must be an airlock somewhere. I'll try your advice today.

 

[sjujnovich]

Re: Mercruiser trim problem

Had a similar problem. Fustratingly tried bleeding the cylinders dozens of times. Turned out the seal was gone in one ram/cylinder causing fluid to leak past it internally (no external leaks). Replaced it with a spare and now works fine. Check the ram seals.

 

[rodbolt]

Re: Mercruiser trim problem

hello yep but also check that the rams can move in the caps. remove the aft anchor pin and rotate the bushing end. if it wont rotate by hand the cap is corroded to the cylinder. the system does not make much pressure going down and is desighned to be self bleeding. but if a seal or checkvalve or cap is to tight it wont work at all.<br /> good luck and keep posting<br /> ps what year/version of this system are you working with ?

 

[727_pilot]

Re: Mercruiser trim problem

Thanks for all the great advice, I have taken a little time off during the holidays and not worked on anything, but it's time to start again.<br /><br />The system is older, not sure but I think it's original and the boat is a '79 model. The trim system is a Mercruiser power trim.<br /><br />Are

 

[Ralph 123]

Re: Mercruiser trim problem

I had the same exact problem on my 79 Formula (pre Alphas/ prestolite pump - if you search the board you'll find it) <br /><br />it is most likely the rear bushing on the trim cylinder has siezed up. You have to remove the end bushing and either run a .750 reamer through the bushing and replace the o-rings or replace the rear bushing.<br /><br />Remove the rear anchor pin going thru both cylinders and see which one does not go back. 1979, replace all of the o-rings.<br /><br />The system in a 79 is also not self bleeding. There is a whole process you have to go through to bleed the system. It is too long to repeat here. Get a copy of the SELOC manual it is described step-by-step in there.