90hp mercury tilt/trim won't go up or hold up under a load.

Eric123

Seaman Apprentice
Joined
Sep 4, 2011
Messages
34
This problem just started out of the blue. It didn't give any initial problems before. And it happens time i put the boat in the water. So it will do it when cold or after running awhile.
Here is what i know:

When boat on trailer:
1. The up and down function works fine on all 3 locations of the boat.
2. The motor will hold up without leaking down for 1 day so far.
3. The motor will lift up with me and my son standing on the lower unit fin, roughly 400lbs.
4. I can't reproduce the motor going down on the trailer.

When in water:
1. While in water sitting still, the up and down works fine.
2. While in water sitting still, the motor will hold up without leaking down.

When in water driving:
1. When i am going slow the motor will trim up and down.
2. When i am going almost at breaking a wake, the motor will not trim up.
3. When getting on plane, motor will not trim up. If i trim it up from a stop then try and get on plane, it will go down.
4. If i trim motor up from a stop and "punch" the throttle it will go down.

When driving on plane:
1 When i am on plane, i can see the trim go up and usually it will hold.
2. Down works fine on plane.

I don't have any issues with the down part. It is my up side that doesn't move or hold under pressure of acceleration.
Is there any orings i need to check the the valve body? If so can someone tell me where and what to check. My boat and motor is a 1999 Bass Tracker with a 90hp Mercury outboard, same year as boat. Thanks
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,342
take the pressure relief screw out and make sure the seal is good....obviously after checking it was tight in the first place. Not easily spotted at first glance, but it’s there. Just go easy when taking it out...the engine will fall down sharp if you do it too quickly.
 

Eric123

Seaman Apprentice
Joined
Sep 4, 2011
Messages
34
ok, i will give that a try after this coming weekend. I have a fishing trip planned and i hate to mess something up and not have time to order parts. But i hope its a simple fix. Thanks for replying.

Do you know where i can get a rebuild kit for that?
 
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