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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10620
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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Have a 1993 mercruiser 4.3 liter my od comes up

Customer Question

Have a 1993 mercruiser 4.3 liter my od comes up automatically when I press the trim down button, if I'm underway I need to hold the trim down button to keep it from coming back up, when I press the trim up button there is no noise or sound is this the trim up solenoid is bad or is also the trim limiter switch, and can I run the boat temporarily until I fix with out burning out the pump itself?
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

Disconnect the trim harness that connects to the trim pump does the trim quit going up? The red circle shows where the trim harness connects. This is the harness for the trim switches.

Customer: replied 1 year ago.
it is connected and clean
Customer: replied 1 year ago.
The boat is in dry dock I m not with it currently
Expert:  Tan replied 1 year ago.

No I need you to disconnect the harness. We need to determine if the trim switch is the problem.

If the trim quits running then we know the trim switch is shorted or you have a skinned wire in the control shorting to power. These trim wires over time will chafe causing them to short between themselves.

If the trim continues to run the the up solenoid is shorted internally causing the trim to run.

Does this make sense?

Customer: replied 1 year ago.
I will test today when I get down to the boat if its the solenoid it will still go down if the harness is disconnected? Or is it in switch? Can I run the boat or will it burn out the pump?
Expert:  Tan replied 1 year ago.

No it will not with harness disconnected. But what you can do is jump the solenoid. If you use the boat with the trim motor running continuously it will burn the trim motor up.

Here is a diagram of the trim wiring. The plug you are disconnecting is the trim switch on the control. C is the up solenoid and D is the down solenoid. To operate the trim up or down jump from E to the small terminal of the solenoid. Blue up and Green down. http://i.imgur.com/bdKoZvd.jpg

Post back with findings and questions.

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