Trim fluid getting into the trim motor?

Question

I recently replaced the tilt/trim motor on my 1990 merc 115 hp. with an aftermarket tilt/trim motor and pump assembly. It ran perfectly the day that I installed it. However, the next day, the motor started running strangely. It wouldn't run smoothly. It would slow-down, then speed back up rapidly. It almost sounded like I had a bad electrical connection. I removed the motor and pump today and a bunch of trim fluid had gotten into the motor. I had heard that sometimes the O ring between the pump and motor can fail and cause this. I was told it was from overfilling the system, but the mercury service manual says that the proper level for trim fluid is that it should be visible when you remove the fill plug. If it isn't you should add more. So it seems that it should basically be impossible to overfill it.

Any ideas why this happends or what I can do to prevent it?

Answer 1

If the trim unit motor and pump are one sloid unit then no fluid should be able to leak between them.

They are sealed with caskets and O rings. If fluid is leaking between the two parts it must be a faulty unit.

Take it back to where you bought it from.

Answer 2

go to marine engines .com and post your question to their panel of mechanics. they have a lot of helpful guys. also try mercruiser or mercury .com.