**How to wire alternator 3.7 mercruiser, alt from 4.3L**

[Lukelona]

Hi guys, I have 3.7 mercruiser I'm gonna do a home built alternator conversion on.
I'm looking at a used alternator I can buy locally for cheap.
It's off a 1991 Mercruiser 4.3L. I believe it's multiple wires on back but I'm not sure how many, as I've only seen a front pic of it.
How would I wires this up on my 3.7? I'll try to post the pic I have in a few.

 

[Lukelona]

I think this is the wiring setup, correct me if I'm wrong. This stuff is new to me. The terms in diagram etc kinda confuse me lol

 

[Lukelona]

 

[Lukelona]

The bottom pic is the actual alternator I'm looking at buying tomorrow

 

[bruceb58]

Just connect the sense to the output which then goes to your battery or starter. Just make a jumper.

The excite goes to your ignition.

Ground goes to the E terminal.

Nothing else gets used unless you have an electric choke which would get its power form the AC tap.

 

[Lukelona]

 

[Lukelona]

Just connect the sense to the output which then goes to your battery or starter. Just make a jumper.

The excite goes to your ignition.

Ground goes to the E terminal.

Nothing else gets used unless you have an electric choke which would get its power form the AC tap.

I have a 3 wire ignition, which do I connect excite wire to?
Also, the ground wire goes to the battery negative or to engine block?
I do have electric choke, so hook my power feed from choke to ac tap?

 

[bruceb58]

That alternator looks different that the Mando alternator you had a wiring diagram before. You need a wiring diagram for it.

 

[Pocket Change]

I think you need a 1 wire alternator. That's what was with my Wagner conversion kit. The instructions told me to combine some wires and disregard others. The 1 wire one has an integral regulator.

 

[Lukelona]

Hmm. Any idea which model it is? Lol it came off a 1991 mercruiser 4.3

 

[Lukelona]

I think you need a 1 wire alternator. That's what was with my Wagner conversion kit. The instructions told me to combine some wires and disregard others. The 1 wire one has an integral regulator.

Yea 1 wire would be easiest but this one is local, and only $40. So if I can wire it, I'd rather just have this one for now
.

 

[Pocket Change]

You might burn something out in the process. Good luck.

 

[bruceb58]

You should have no issue getting this one to work once you find the wiring diagram for it. I dislike 1 wire alternators. They need to many RPMs to kick in.

 

[Lukelona]

You should have no issue getting this one to work once you find the wiring diagram for it. I dislike 1 wire alternators. They need to many RPMs to kick in.

That's what I heard also, which was why I didn't care that it wasn't a one wire.
I'm looking for diagram now

 

[Lukelona]

Mercury marine part #19685. Can't find an exact diagram for this part number, but it comes up same as diagram above.

 

[Lukelona]

 

[bruceb58]

For the two wires going into that regulator, one will be the excite and one will be the sense. For the time being, you can connect them both to the ignition. If the ignition has a drop between the battery and the sense, the alternator will put out a higher voltage than it should. You can experiment later if you want to find out which one is which.

Hard to tell from your picture. What color are the wires? Likely, the sense will be red.

 

[Lukelona]

For the two wires going into that regulator, one will be the excite and one will be the sense. For the time being, you can connect them both to the ignition. If the ignition has a drop between the battery and the sense, the alternator will put out a higher voltage than it should. You can experiment later if you want to find out which one is which.

Hard to tell from your picture. What color are the wires? Likely, the sense will be red.

It appears that one is red, one black. Then the thicker orange should be positive to starter, and the thicker black gets grounded to engine block?

So just splice the excite and sense together and run them to ignition "on" terminal?

I appreciate the quick response as I will be buying this alternator locally tomorrow at noon and would like to know how to have it wired!
Thanks for all the help

 

[Lukelona]

Also, how do I get my voltage gauge to work when I re-wire? Is the sense wire supposed to go to the gauge?

 

[bruceb58]

If you haven't bought it yet I would just buy a new one.

Voltage gauge just goes to your ignition switch.