TOPIC: Wiring a stack

Wiring a stack 11 years 2 months ago #83789

All Dunn II
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I am changing from a '63 Merc 850 to a '77 1150. In order to match the harness in the boat, I need to use the motor side of the plug from the 850 on the 1150. Will it work to just hook up "red to red" and "green to green" ect. I looked through the wiring diagrams for both and the wires seem to go to similar components. I just wanted to be sure so I don't fry the switch box or some other high dollar parts.
Thanks,
Bill

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Re: Wiring a stack 11 years 2 months ago #83793

ed-mc
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Bill, things should generally match up, stuff like choke and starter solenoid are simple and you can check with a meter or test light.

The switched +12V wire (white) which fed the ballast resistors on your old 850, will now need to be connected to the white terminal on the Starboard side of the switchbox. NOTE: make sure you don't connect any power leads to the distributor-side of the switchbox, else you'll likely fry it!

You'll also have to rig a jumper to provide a constant +12V supply to the red terminal of the switchbox (same side as the white switched power).

You could use the battery side of the big terminal on the starter solenoid, just crimp a 5/16" (as I recall) lug on a hunk of red primary wire (#12 would be suitable, as probably would #14), and an appropriate-sized lug on the other end of the wire to connect to the switchbox (#10 screw I think).

You can do the jump up real "clean" by putting a half-inch or so of shrink-sleeving at the wire/lug area. Instead of using insulated crimp connectors, I'd recommend an uninsulated lug, crimped and also soldered. It'll provide a better electrical connection to the switchbox.

Another source of unswitched +12V inside the powerhead would be the red wire connected to the rectifier; you could attach one end of your jumper there, instead of at the solenoid. Your preference; electrically either location would be the same.

I don't recall the 850 having a tach output built-into the harness, so you'd have to figure out something for that.

An independent wire could be run from either of the yellow-stator-wires at the rectifier, up to the driver's area to provide tach-sensing to a "modern" 12-pole-alternator-type marine tach.

HTH...........ed