Trim creeps down when riding

[a327vette]

80 Dixie 199 super skier with alpha 1 outdrive. When boat is planed out, you have to keep bumping the trim up every 3 min or so. It doesn't go down far, but it does go down. The cylinders were rebuilt, and its still the same. Could the pump be leaking? Everything is dry, so its not an external leak.
Thanks

 

[thumpar]

Re: Trim creeps down when riding

It could be the valve in the pump. Does it go down when it is on the trailer?

 

[a327vette]

Re: Trim creeps down when riding

It could be the valve in the pump. Does it go down when it is on the trailer?

I'll have to check, I never leave it resting on the hydraulics so I don't know

 

[old islander]

Re: Trim creeps down when riding

I just sorted out the same issue on my boat. The problem for me was trim creeping down both on the trailer and while running. Mine was the check valves in the bottom of the pump housing. I have a 1977 MC1 with the old style Prestolite pump set up. I'm not sure what your pump set up is being a 1980. If it is the old style pump the valve assembly is no longer avalible. I got a used one from a member here on the site. You can also buy a new style pump set up that replaces the old one, however it is a bit expensive. About $700. I have found the old style valve assembly on Ebay quite often. The going rate for this seems to be $150-$250 used, but no guarantee it still works. Ebay is kind of a crap shoot.

 

[a327vette]

Re: Trim creeps down when riding

Thanks old islander, it looks like that may be my problem. It does leak down on the trailer, so looks like I need to look into the pump valves I guess.

 

[hoot]

Re: Trim creeps down when riding

Some pumps have a valve body under the motor/oil reservoir if this is your style of pump. In this valve body are several ports and o-rings. On occassion, the o-rings can split and leak. Check the rings.