View Full Version : Alternator Wiring ?

05-10-2011, 08:47 PM
I am in the middle of rewiring the '86 C22. Boy do I have stories !!! What a mess.

The schematic shows that the Red/Pur (+12 from breaker) and the Pur (from ignition on, fed by breaker) are both connected to the field.

I am guessing those boxes are diodes or the purple would be energized all the time.
I can understand that the Red/Pur would keep the field energized if the ignition was turned off while alternator still was spinning.
But since the Pur is supplied with +12 from the breaker then thru the ignition switch, I don't see any reason for it.

It only makes sence if it's a hold over from the ext. voltage reg days.

Can anyone enlighten me ? :bonk:

05-10-2011, 11:33 PM
It serves a purpose! http://www.marinemechanic.com/site/page250.html

05-11-2011, 12:23 PM
That schematic shows (very poorly) an ext. voltage regulator.
In that case the Pur and Red/Pur are NOT connected to the same terminal.

I haven't gotten to the engine bay yet. Still having fun unravelling the mess under the dash :nilly:
It's amazing what can be done in 25 yrs by people who are not trained or talented !
There must be 50 splices using cheapo crimp barrel connectors, with all different guages and colors :bonk:
The same wire will change colors and AWG several times along a 5' run !!!

Yes, I am trained and have worked 30+ yrs in electronics, electrical control systems, computers, and data networking.

Thanks MOP

Donzi Vol
05-12-2011, 11:59 PM
My suggestion is to get a single wire alternator, wire it directly into the charging system, and then address the dash. I may have some here to disagree with me, but this method cuts out a lot of guess work and is fairly easy to rig. The only problem that I had was continuing to buy the incorrect alternator for the job. User error...

Once the alternator is in place, you can address what's under the dash. Mine was a bird's nest too. Just remember that the red is hot and the purple acts as a daisy chain to connect the gauges.

Good luck!

05-13-2011, 07:11 AM
Another solution is to purchase one of these universal Merc/Omc engine wiring warnesses. They come w/the plug, correct size and color, including the alternator wires!!!!!, and it's 6' long. The good news is the price is less than $80.00.


The corresponding "round to square" piece, 20' long is less than $100.00.


And then the pigtail for under your dash, 10' long, is less than $30.00.


I went this route on the TR and it saved me ton of trouble. I didn't use the square connectors for the dash end because I used terminal strips, but the wire sizes and colors were correct, new, and in good condition.

05-14-2011, 03:48 PM
The auto industry is way ahead of the marine sector with the 1 wire alt !

I spent the last couple days pulling out all of the unused wiring. In this
entire mess 5, yes 5, circuits were still in use. The rest were connected at one
end or the other and some was just in the bottom of the boat.

Notice the square trailer connector and all of the cheap barrel connectors. Half of
which the wires fell out when removing. Almost all were very corroded.

I am now taking out the engine harness. The funniest part is the wire that connects +12 (starter post) to the breaker.
It is a 14 awg (automotive) that someone put inside of a thick red sleeve and crimped big lugs on each end !!
Totally faking it to look bigger. There are even purple ground wires !

I haven't even addressed the stereo speakers that have 28 awg wire.

05-14-2011, 04:57 PM
You're correct on every point.
Every one of these boats I've done, I've ripped it all out and started over.
Just think of the number of owners and people who've worked on it in 20 plus years!

The one thing I don't care for about the one wire alternators is you have to rev the engine to 1,200-1,500 RPM to exite them.
I had one on the Minx and it was OK. I bought a new Mando for the TR and I'll use all the wires. I wanted to see how different the experience is.

05-14-2011, 05:24 PM
Here's a rear view of the Mando. The wires and terminals are clearly visible.