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Author Topic:   1989 OMC Sterndrive Trim-Tilt Wiring
madmac62 posted 08-04-2010 09:10 AM ET (US)   Profile for madmac62   Send Email to madmac62  
I am helping out a friend with my Automotive Experience and while the electrical problem solving for voltage drop etc. applies I am lacking some specifics. His trim completely quit working one day. The switch works fine and so I traced the wiring back to the lift pitons in the back where I found three wires running to them. RED, BLUE, And GREEN. The blue wire split into a female bullet type connector that was near a solenoid but was unhooked. When twelve volts(fused) was applied the outdrive lifted only. I cannot find or see where this plug in came from. Does anyone have a wiring schematic for this type of system. Or can you tell me if this connector even is attached???? Maybe I should be looking at the lift solenoid instead??? Thanks for any help you can give.
seahorse posted 08-04-2010 11:22 PM ET (US)     Profile for seahorse  Send Email to seahorse     
I don't know of a wiring chart online, only the one in the factory service manual.

They are wired like an outboard trim system with a 2-wire motor and dual relays. The relays ( some have a single module containing 2 relays) each have a NC contact for ground circuit. When one relay is activated power goes through that relay to the trim motor and returns through the ground contact of the opposite relay.

red - B+

blue - up wires

green - down wires

Simplified schematic diagram of trim control wiring

jimh posted 08-08-2010 10:19 AM ET (US)     Profile for jimh  Send Email to jimh     
[Added in-line graphic showing simplified schematic diagram of typical trim-tilt electrical control circuitry.]
jimh posted 08-08-2010 11:58 AM ET (US)     Profile for jimh  Send Email to jimh     
That is a splendidly drawn schematic diagram. If fulfills the purpose of showing the circuitry in a manner which helps understanding of the function. Too often schematic diagrams are no longer drawn in a manner which helps one understand the intended function of the circuit, but this one is a beauty. Thank you to seahorse.
andyski posted 08-20-2010 09:01 AM ET (US)     Profile for andyski  Send Email to andyski     
[Are] there in line fuses? The outdrive cannot move up or down. [T]here is no power at throttle arm.
jimh posted 08-20-2010 09:32 AM ET (US)     Profile for jimh  Send Email to jimh     
The control circuit current is typically supplied through a fuse, however that same fuse also supplies other circuits, too, and if the fuse were blown there could be other circuits affected. A bad connection could also cause an interruption. Trace the circuit path back from the remote throttle handle and check for discontinuities.

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