tilt & trim slams down

[eric1111]

85 mercury tilt and trim goes up and down. leaks down pretty quickly. removed and replaced all o rings in all three cylinders and refilled with new atf and removed all air? still leaks down,but slowed down..took it to the lake to test another problem and will not raise under load 5 mph. but i can hear the motor running. i stopped and raised it up a little then hit the gas, the engine slamed down hard... mine is the square style motor.. heard there maybe a check valve in the pump body sticking. removed motor and pump body, but don't see anything sticking..any suggestions would be helpful

 

[j_martin]

Re: tilt & trim slams down

You have something relieving the pressure. It could be a loose/damaged manual valve, or a pressure relief valve with a bad seat or broken spring, or just a totally fried pump. At any rate, sumpin aint rite, and it should be obvious when you see it.

hope it helps
John

 

[Chris1956]

Re: tilt & trim slams down

Eric, If the trim leaks down, it is usually either the piston seals or the check valve. My experience has shown it to be the piston seals.

You might be able to isolate and test it, if you have the twin hydraulic cylinders type. Remove one set of hoses from one cylinder, from the pump. Plug the holes. Now run the trim up and see if it leaks down. If so, try the other cylinder. If that too leaks down, you either have two bad piston seals (unlikely) or a bad check valve.

 

[eric1111]

Re: tilt & trim slams down

thank you for giving some feed back, it all appricated!
unfortantly mine has 1 primary and 2 secondary cylinders..i did think the same thing the pisions seals were bad..i put new seals on pistions and caps, also no scaring on cylinder walls was found..this did slow the leak down problem, but did not stop it. there are no hoses attached to cylinders to isolate down, eveything is internal.

 

[lilmandavis]

Re: tilt & trim slams down

Examine the check valve thats likely the prob, id say just replace that too. does the pump sound like its struggling when trying to tilt up?or does it sound like there is no load on it?

 

[eric1111]

Re: tilt & trim slams down

it sounds normal to me...i pulled the pump apart and looked at check valves. one of the needles has an o ring on the seat and the other does not...a bet this is the problem..thanks again for the advice..