Mercruiser Trim motor problems

Old 06-02-04, 10:57 AM
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Question Mercruiser Trim motor problems

I have a mercruise stern drive. The trim works both up and down while sitting on the trailer or in the water while sitting still. Trim will go up but not down while under way. Voltage is good at motor. I have heard that I may be low on oil, but I don't know how or where to check it. Also what kind of oil do I use?
Old 06-03-04, 07:10 AM
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Hello: joeduby

The hydraulic fluid holding tank should be located on the engine. Same type as a vehicles power steering system. Or may be a seperate pump likely to be located in the engine compartment or mounted on the transoms inner wall.

If the boat steers well, not likely the trim plates are a combined system with the steering. Most likely a seperate system. Look for the electric pump on the transoms inner wall.

One of several possible reasons trim tabs not working while in motion.
Low fluid.
Weak pump.
Fluid restriction.
Worn out seals in hydraulic cyclinders.

Wornout seals in hydraulic cyclinders do not allow enough fluid pressure to overcome the force of the water pressure against the trim tabs. Cyclinder rebuilds are than needed.

Check with your local boat repair shop for additional information and fluid type(s) to use. Trim tab hydraulic cyclinder rebuilds require specialized skills, knowledge and tools to successfully rebuild them. Best left to the pros.

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Old 06-19-04, 07:09 AM
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I had a problem with my outdrive trim, it would not go up or down in or out of the water. But it sounded like the pump motor was making noise. The manual called for SAE10W-30 motor oil to be used in the pump reservoir. Filling it solved my problem.
Find your hydraulic trim pump, remove a plug hole scew on the pump reservoir and fill with oil.
Maybe water pressure from the forward movement of the boat stops downward travel of trim. While out of the water see if trim travel can be stopped with a little pressure check for both up and down,this may tell you why it doesn't trim down, but I can't say how to fix it,

good luck

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