Mercury trim and tilt leak down

[fishingman]

Hey everyone, I'm trying to figure out if my 1988 mercury 90 HP outboard has a bad seal in the hydraulics or a bad trim and tilt pump. I just picked up the motor, and know very little about it except its sat for last 3 years. Anyway, when I trim up, the motor wants to fall right back down. Once all the way up, the motor will fall down through the tilt and both trim cylinders in about 20-30 seconds. There are no external leaks and I checked the fluid level and manual release screw seals. I was talking to a local shop about the check valves going bad, but he said for it to fall through both the trim and tilt cylinders would mean all the check valves were bad and he thinks it more likely the pump. I removed the whole unit from the outboard and I am thinking about dropping it off at the shop, but I know that will get costly.

Anyway if there a way to diagnose if the trim and tilt motor and pump is bad? Its one of those eaton square pumps i believe. Or if anyone has any other idea's, I'd love to hear them. Thanks

 

[fishingman]

Re: Mercury trim and tilt leak down

Does anyone know of anything in the hydrualics that could go bad and make all the cylinders leak back down, or is the pump the most logical problem?

 

[woody66912]

Re: Mercury trim and tilt leak down

I think you will have to replace the starboard trim ram. Seen lots of these years a go. You can get the spanner wrench from motion pro.

 

[fishingman]

Re: Mercury trim and tilt leak down

Will that one ram cause the tilt ram to leak down as well?

 

[woody66912]

Re: Mercury trim and tilt leak down

Yes I can't quite remember why this is but Trying to explain the inner workings of a t-n-t unit is very hard.

 

[aussieflash]

Re: Mercury trim and tilt leak down

I would strip it down and replace all o rings and seals.Kits are still available online.One kit for trim rods only and the other for pump and main ram.
Check valves are located in main ram and Port trim rod.Replacing starboard trim will do nothing,unless its damaged.Its the port trim that usually needs check valve cleaned or rod replaced.

 

[woody66912]

Re: Mercury trim and tilt leak down

I would strip it down and replace all o rings and seals.Kits are still available online.One kit for trim rods only and the other for pump and main ram.
Check valves are located in main ram and Port trim rod.Replacing starboard trim will do nothing,unless its damaged.Its the port trim that usually needs check valve cleaned or rod replaced.

thanks for the correction I started to second guess myself on witch ram it was.

 

[fishingman]

Re: Mercury trim and tilt leak down

Before breaking it down to rebuild the cylinders, does anyone know if theres a way to test the pump to see if thats a problem?

 

[RRitt]

Re: Mercury trim and tilt leak down

Before breaking it down to rebuild the cylinders, does anyone know if theres a way to test the pump to see if thats a problem?

can't be positively isolated without doing more work than a rebuild. The path of least resistance is to just rebuild it.