290 trim issues

I have a few issues with my trim. For one the outdrive won’t stay trimmed. It will slowly go to full down while underway. It will stay trimmed at rest all day. Just won’t stay at speed. There doesn’t seem to be any leak anywhere as I don’t need to refill the reservoir.

The other issue I have is the gauge is stuck on -88. I have the older square display that had a few green lights to show it’s trimmed in running condition then went to red I think when it was too high. It also used to stop before raising too far up and then I would have to keep pushing another button to get it to raise more. Now it will come all the way up without having to push that button. I’ve looked at all the connections and unplugged and plugged back in any harness I could find with no change. Any thoughts?
Robert

The leak that is causing the cylinders to retract under load may be internal.
Could be a cylinder piston seal, or it could be the valve at the pump itself.

RicardoMarine said:

The leak that is causing the cylinders to retract under load may be internal.
Could be a cylinder piston seal, or it could be the valve at the pump itself.

Click to expand...

thanks for the response. I misspoke. The outdrive actually does slowly drop on its own at rest (Like an inch or two a day). Any way of troubleshooting where the problem might be? Also how to trouble shoot the gauge? I’ll take it in in the off-season (January/February) but have a few months left on the ocean so would be nice to figure out the problem before then.

While the pump supplies the hydraulic pressure to operate the two cylinders (while being operated), the pump system "checks" the hydraulic fluid via a valve (while not being operated).
These valves can leak, causing the cylinder to retract under load.
In many cases a good valve cleaning gets things working again.

https://www.marinepartseurope.com/en/volvo-penta-explodedview-7749307-44-10690.aspx


There is also a manual release valve. Check that out also.

Thanks. The trim pump on the boat isn’t the Volvo one. It got replaced somewhere down the line by the previous owner with one that’s usually on Mercruisers. (SAE J1171 Marine). I’ll see if I can find a parts diagram and clean the valves. The trim pump wouldn’t have anything to do with the gauge not working could it?

I guess j1171 is a marine standard. Anyway it’s not the original trim pump per the documents. From the above picture is the black screw in between the two hoses the manual release valve?
-Robert

Rscottdds said:

Thanks. The trim pump on the boat isn’t the Volvo one. It got replaced somewhere down the line by the previous owner with one that’s usually on Mercruisers. (SAE J1171 Marine). I’ll see if I can find a parts diagram and clean the valves. The trim pump wouldn’t have anything to do with the gauge not working could it?

Click to expand...

No... the gauge is operated by the sender unit, of which is operated by the rack gear that is on top of the helmet.

Rscottdds said:

I guess j1171 is a marine standard. Anyway it’s not the original trim pump per the documents. From the above picture is the black screw in between the two hoses the manual release valve?
-Robert

Click to expand...

That would be for the Volvo Penta pump. You'll need to look at the Merc pump.


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Thanks for your help. Really appreciate it. What about the trim limiter issue? Do you know what could cause the outdrive to come all the way up now instead of stopping first before pushing another button to have it come all the way up? I’m sure it’s designed that way so you can’t accidentally trim it out of the water while underway.
Robert