WIring harness for 1978 50HP

tgpfloat

Seaman Apprentice
Joined
Jul 30, 2007
Messages
42
I have a 1978 mercury 50 hp outboard.
One wire (a big red one) attached to the rectifer has heavy corrosion and looks bad. From my manual this is the wire the heads to the + side of battery and cannot be working very well to charge my battery. I thought of splicing a wire in but was told by many this is a bad idea. It was recommended replacing the internal wiring harness. I found one online for about $100 bucks. didn't seem too bad. Is it difficult to replace? Where does the other end of the harness plug into? It appears from the pictures to have a brass prong plug on one end this is the end I do not know where it goes. I was thinking I need to replace the rectifier while I am at it.
What controls the rectifer output so the battery does not get over charged?

Thanks

TGPfloat
 

rtpassini

Chief Petty Officer
Joined
Nov 27, 2008
Messages
508
Re: WIring harness for 1978 50HP

how big? i dont have any big wires from my rectifier. they are all about 16 ga...
 

Moody Blue

Captain
Joined
May 24, 2004
Messages
3,136
Re: WIring harness for 1978 50HP

"I thought of splicing a wire in but was told by many this is a bad idea."
Depends on the individual circumstance. Most harnesses of that vintage have significant deterioration of the insulation and require either replacement or repair. If you are handy AND you can cut the original wires back far enough and find "good" wire then you may be able to repair it.


"Is it difficult to replace?"
No, easy to replace. Harness is captured with a clamp and 2 screws into the lower cowling. Tag each wire and note the color and location before removing the original wires.

"Where does the other end of the harness plug into? It appears from the pictures to have a brass prong plug on one end this is the end I do not know where it goes."
Plugs into the wiring harness that runs from the helm control box.

"What controls the rectifer output so the battery does not get over charged?"
Nothing.
 
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