1986 Mariner Magnum 150hp 6cyl Trim Screw/Motor loosing pressure slowly

[Coxwain]

My trim motor will trim up and down the motor. However, when I trim it up, it will eventually loose the pressure and settle back down.

I have played with the manual trim screw and if I loosen it, it will lower the manual and then tighten it will stop.

I would like to replace the trim screw but there is a washer on the inside of the housing so that I cannot remove the screw.

BTW there has never been any fluid that has leaked from the trim motors onto the driveway or in the water.

Two questions.
1. How do I remove the retaining washer and it seems to be a full circle washer.
2. If the screw isnt the problem, then what else might the problem be?

B176526 serial number

[JOE54]

clamp brkt gota come off on that side for relief valve remove, likely you have a valve body problem ,shuttle valve not seating inside pump,replaceing pump and mtr assembly cures this WARNNING $$$$$$$$$$$

[Coxwain]

Can you rebuilt it?

[JOE54]

no oem parts available and not recommended, aftermarket pump and mtr assembly

[straffordengineer]

Can you rebuilt it?

O-ring kits are available but check valves aren't. I suspect you just have a bad o-ring but you won't know until you rebuild it. A o-ring kit for the main cylinder is 25-41478A1 and costs about $85 and an o-ring kit for everything else is 25-48462A4 and costs about $100. Complete new pump assembly runs about $1300.

[Coxwain]

https://www.dbelectrical.com/product...75n-99186.html
I found this aftermarket motor and pump so I will give that a try.

I'm going to try to replace the o-rings too.

Turns out the motor has reached end of life. The armator is fine, but the brushes and the brush holders are all crap.