Force Outboard Tilt/Trim Issue

unfilthy

Recruit
Joined
Sep 10, 2015
Messages
1
I have a 1997 Force 75hp ELPT that won't stay trimmed at wot. It will plane out and I can trim into the sweet spot, but then it trims back down on its own and begins to bow plow. I will trim back up into the sweet spot at this keeps repeating. I thought this may be because of an air bubble so I drained the system, refilled, and bled.....problem still occurs.

The system only has one big ram that operated as both tilt/trim. There is/are no smaller trim ram(s). From the tear down diagrams this seems to be correct but a little confusing as the single large ram seems to have a hard time holding the trim at wot. There is no bleed down while on the trailer.

Could this be an air bubble in the ram? Is there suppose to be a lower trim limit set rod like in the no PT versions? There are holes for the rod as both versions use the same bracket. Just a little irritating as I'm trying to test a new prop since it was under proped for my setup when I bought it.

Anyone have any ideas or experience with these force outboard single ram tilt/trim models?
 

Boat Doctor1

Petty Officer 2nd Class
Joined
Sep 29, 2012
Messages
123
Just my guess?= Id look @ the valves (seals) on the unit. these "Valves" if bad will by-pass fluid under pressure! Likely will need new ones.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,183
Your motor came with 2 different style pumps, pics?
The rams are the same.

The cylinders can be rebuilt.
Contact a Mercury dealer for the seals.

The pumps can be rebuilt too but it's usually easier to replace the hyd. pump..
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,605
Sounds like some "O" rings or seals are in need to be replaced now. Sounds like bleed-by with the piston...
 
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