1995 Force by Mercury 40hp power trim problem

[xcavater]

Just bought this boat.
Everything worked as it should, I raised and lowered the drive countless time while in the driveway.
Put it in at the ramp and as I was backing off the trailer the motor raised up as if the lock rod on a manual trim wasn't in.
Ran the boat to test and the drive won't tilt up and down.
Get boat on trailer, found fuse blew, answers why drive wouldn't go up or down.
With the boat on trailer and the motor in the down position, I can lift the motor up by hand (same thing as putting it in reverse), let go, motor drops back to original position.
If I raise with the trim motor, I can do the same thing and it will drop to it's trimmed position.
Will not go down without using the trim controls even if I push on it so it's not bleeding down.
I've checked the o-rings on the manual release they are good.

 

[RRitt]

Re: 1995 Force by Mercury 40hp power trim problem

is the trim motor spinning properly?
if the motor desont' spin then system won't raise and lower correctly.
is the trim system topped off with fluid as per manual?
1995 had a memory piston so low fluid can give almost any result depending on where air bubble gets trapped.

if the motor spins as it should, if the system is topped off as it should, and if the orings on manual release are good ... but the system
won't raise & lower properly (or won't stay) then it is in the pump. Try removing the cap next to manual release and putting two #2 SS shims underneath the spring. sometimes that helps.

 

[xcavater]

Re: 1995 Force by Mercury 40hp power trim problem

The motor sounds like it is turning at a good rpm. The drive moves as it should. I'm thinking it was the memory piston, but why in one direction. I'll change the fluid and see if it makes a difference.
What would the washers under the spring do?
Thanks