Trim won't stay DOWN while underway.

[PDG]

I have a 19', 1974 sea ray with a Mercruiser Outdrive. Recently I've noticed my trim seems to creep "up" under power and the boat begins to "porpoise" shortly thereafter. I can press the trim down button for 1-2 seconds and it resolves... then 10 second later starts creeping up again.

 

[Texasmark]

Low fluid, piston "packing" leaking on one or both outdrive cylinders would be my guess. Being a vintage boat, possibly the pump needs an OH too.....but I'd go for fluid level check, then outdrive piston repacking, then worry about the pump.

 

[PDG]

Thanks Texasmark. I will check the outdrive cylinders. I had checked the fluid when this started and it looked good. I have a dumb question ....Is there such a thing as a partially spun hub? I ask because wouldn't the propulsion of the prop keep the lower unit from raising at all while underway? I didn't know. Thanks for your time.

 

[Chris1956]

I would think that the prop thrust would keep the trim down. I would look for a loose connection, perhaps at the up switch. I suspect the up circuit is activating as the boat cruises.

A test is to disconnect the power trim and then try cruising. If she trims up w/o power connected, it is a mechanical issue.

 

[Texasmark]

I would think that the prop thrust would keep the trim down. I would look for a loose connection, perhaps at the up switch. I suspect the up circuit is activating as the boat cruises.

A test is to disconnect the power trim and then try cruising. If she trims up w/o power connected, it is a mechanical issue.

Good point. Makes more sense than what I said about cylinders leaking...to solve his particular problem.....must have had a brain pfart. Grin

 

[PDG]

Thank you. Much appreciated. I will check the up switch and troubleshoot it.

 

[Chris1956]

The toggle style switches can get water in them that completes the circuit in the up direction.

 

[Texasmark]

The toggle style switches can get water in them that completes the circuit in the up direction.

If that turns out to be the case, shop around. Rubber encased toggles are available for wet locations. Ebay is where I personally would start and just ask for sealed toggle switches, or booted toggle switches. I assume you will be looking for a Single Pole, Double Throw (SPDT) Momentary ON.