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

[Lukelona]

I already committed to buy it just have to pick it up today. You don't think it'll work?

After researching alternator wiring and from what you said earlier Bruce, I think it should be-
Connect red to orange via jumper,
Run black wire to ignition
Thick black to engine or battery ground

Does this sound right?

 

[bruceb58]

Yes..sounds right.

 

[Lukelona]

Ok, my next questions will be about regulator wiring and how to remove it.
I know to cut the stator wires and cap them off well, install barb fitting in place of regulator to complete cooling hose.
I know the purple wire on regulator is the keyed 12v according to diagram. Do I just cap the other wires and maybe use the purple as keyed 12v?
Purple should go to the excite stud on alternator?

 

[bruceb58]

Purple should go to the excite stud on alternator?

Yes

 

[Lukelona]

Picked up the alternator, it came with the harness also still connected so at least I can see how it was wired previously. Going to mess with it now. I still gotta fab brackets for it too. It came with the one adjustment bracket so maybe I can make that one work and make one other bracket. I'll post pics soon

 

[bruceb58]

You a welder? That would be the best way to fab them. Would also be nice to have a plasma cutter or cutting torch.

 

[Lukelona]

No lol wish I was, if I welded them they'd probably fall off just from the weight of alternator haha

But I can bend, and bolt just about anything! Lol
I used the one bracket that came with it, couple washers for spacers, and it works ok for the lower.
Used 1/4" x 1' flat bar and bolted to top mount and behind ps pulley onto pump.
It's on there, but don't like it as is. It's gonna vibrate to much.
Went and got more flat bar, I plan on bending to a 90? at one end bolting to top mount flat bar I made and bolting other end using intake manifold bolt. This should sturdy it up good I think.
Then I have to test fit for a belt, and wire it up.

 

[Lukelona]

don't laugh how ugly it is lol
It's just a mock-up right now. I'm gonna cut it down, round the ends and edges and paint the brackets.

 

[Lukelona]

 

[Lukelona]

 

[bruceb58]

Your biggest issues are going to be belt alignment, vibration under load and how are you going to tighten the belt. Thats where a friend with a plasma cutter, like me, comes in handy!

 

[Lukelona]

 

[Lukelona]

Your biggest issues are going to be belt alignment, vibration under load and how are you going to tighten the belt. Thats where a friend with a plasma cutter, like me, comes in handy!

I eyeballed it the best I can for alignment, I think it needs one not washers spacers. I'll know more when I get the right belt.
I'm hoping the ps pump will still adjust belt.
And i wish I had a plasma, I'm struggling with sawzall and grinder lol

 

[Lukelona]

If vibration occurred , would it break the timing cover I have it mounted to? I'm kinda nervous about that now! I'll have to overengineer the craps out of it to have NO vibration lol

 

[Lukelona]

Ok got it all mounted, got new belt on wired orange to starter battery lead, and the red wire to same stud on starter. Wired purple wire to electric choke.

Started, runs and charges 12.8 at idle, 13.9 revved a little bit. Checked everything and noticed alternator is getting hot. Just about to hot to touch. Also orange wire is a little warm, but I think it's fine.

My battery is charged at 12.4 volts right now, but it may have charged some when running it.
I'm wondering if batteries were low and alternator is hot from trying charge them, or if something's wrong.

What could be the issue? I've busted my butt on this thing so is disappointing that it doesn't seem right

 

[bruceb58]

Alternator will get hot if its putting out a lot of current. A fully charged battery will be at 12.6. Measure the battery voltage after it has been sitting after 30 minutes after charging has ended.

 

[Lukelona]

Battery voltage is at 12.15 onthe brand new battery, and 12.04 on older battery. This is after sitting since earlier today.
so they were probably around 12v when I started it earlier. Would that make alternator hot?
Could it be bad ground? I ended up grounding to the brackets I made.
Also, I've read stuff about a resistor in the purple wire I believe? I'm not sure what this is or if I have one. I know I didn't add one myself.

 

[bruceb58]

There should be no resistor in the purple wire going to the alternator. It needs full 12V. Your ground is likely fine. Just th eground from the brakets themselves is good enough. The ground wire just makes sure.

Your battery is around 50% discharged if it's close to 12V. That is why the alternator is getting toasty.

 

[Lukelona]

Ok charged the batterywith 6amp charger for about 30 min just to test. Once battery was up to 12.7 I started boat (without charger) and all seems well now! Alternator is only getting normal warm temp. Not HOT like it was.
I think we're good to go! I'm gonna install one brand new marine battery to replace the one older one also.

With the extra bracket i added it just barely shows vibration. Should it be rock solid or is very little vibration normal ?
Big thanks to Bruceb58! I really appreciate all your help and patience as you walked me through this learning process!

 

[Lukelona]

Bump