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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10632
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I need a wiring diagram for a 1976 mercruiser trim pump. Im

Customer Question

I need a wiring and hydraulic line diagram for a 1976 mercruiser trim pump. I'm not sure if the solenoids and wires from the trim switch are wired correctly. Its a black metal trim pump, with the square base. It doent have the plastic reservoir. I also did a motor swap. I took my 1979 OMC 230 (chevy 305) and mated it with a mercruiser 888 sterndrive off of a 1976 Bonanza. The Bonanza had a straight 6. I stuck the both into a 1996 Bayliner 2050. I also converted the Merc Transom plate to an alpha 1 v-8 transom plate and kept the rest of the lower unit pre alpha. My next question is do I need to change the distributor or the ignition since mercruiser hass the "shift interrupt switch"? Do I need to change any part of the ignition? Does anyone have a wiring schematic on how to hook up the shift interrupt switch? This is the last step on my hull up build. Im almost broke and a Marine Corps Vet. It's my 2nd summer out of the Corps and I wanted the boat done by the 4th, Well hopefully I can get a quick diagram and enjoy her tomorrow! Thanks in advance!
Submitted: 6 years ago.
Category: Boat
Expert:  Tan replied 6 years ago.
graphicHere is a diagram of the engine circuit. I am getting the diagram for the trim. If you use the mercruiser ign components you will be fine.One solenoid for trim or two solenoids.

Edited by Tan Partin on 7/10/2010 at 5:30 PM EST
Customer: replied 6 years ago.


Thanks for the diagram, its nice to finally see it. I figured the trim wiring out myself and I believe the hydraulic line. I actually bypassed the reverse lockout system just to check to make sure the pump had good power. Now I have to figure out the hydraulic lines coming from the shocks to the reverse lockout system and to the pump. I switched the 1976 shift lever out with a newer alpha 1 type controller. Long story short I took the '79 omc 230 engine mated it to a 1976 Merc 188 sterndrive that had aa inline 6 attached. The transom plate itself is for a v-8 its an Alpha 1 from 1995. So I had to block off a passageway, and do some major modification to mount the trim pump and the bracket for shift control, reverse lockout, and shift interrupt. New Hydraulic lines and all.

Thank you.




Expert:  Tan replied 6 years ago.
Great here is a diagram of the hoses. The hoses aft # XXXXX & 6 are for down, the hoses forward are for up. The line inside the boat # XXXXX down to the reverse lock # XXXXX up to the pump. The nylon line to pump.Diagram of Mercury Mercruiser Parts R-MR-ALPHA ONE (Sterndrive) 1983-1990(NNN) NNN-NNNNTHRU 0D469858 TRIM CYLINDERS AND HYDRAULIC HOSES Diagram
Customer: replied 6 years ago.


I already have the bracket hooked up on the stern drive. What I was looking for was a picture of exactly which hose goes to which fitting on the pump, reverse lockout and trim limit. the trim limit has 2 lines, and the pump has 2 fittings. the trim lockout has 4 fittings, 2 ofthe fittings on the reverse lockout have a clear line that connect them. Do you have something that shows that exactly?


Expert:  Tan replied 6 years ago.
graphicHi Shane, Here is the routing of the hoses this is not the greatest diagram.

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