Bad alternator.

[cecho]

My alternator is bad. I'm planning on getting a cheap 100+ amp 10SI marine rated Delco alternators available for sale on ebay. I bought a pair of them a few years ago for a twin engine boat I had and they seemed to do rather well, but I'd like some opinions. The alternative is to get a repair kit for mine (Assuming they make one for the model I have). I've never rebuilt an alternator, but I can't imagine it'd be too difficult.


New Delco Marine 10SI Alternator Mercruiser 3 Wire 110 Amp | eBay

 

[Eric 3.7LX Alpha 1]

Re: Bad alternator.

I have that same alternator from them.

About 3-years now....knock on wood!!

 

[cecho]

Re: Bad alternator.

That's good to know.

 

[cecho]

Re: Bad alternator.

The alternator in my manual looks nothing like the alternator in my hand.

I've got 4 wires coming off my alternator. Am I correct with these wires?:

Large red (Output I assume)
Large Black (Ground I assume)
Small Red (12 volt battery sense?)
Small White (Excitation Lead?)(Is this 12 volts when ignition on?)


I don't think the 10SI has a spot for a ground wire. I'm going to assume it's okay to bolt that to the alternator itself or a spot on the engine. Or should I remove it? Is there another electrical ground located elsewhere?

 

[Don S]

Re: Bad alternator.

Large red (Output I assume)
Large Black (Ground I assume)
Small Red (12 volt battery sense?)
Small White (Excitation Lead?)(Is this 12 volts when ignition on?)

Yes to all.

Does your boat have an ammeter setup or a volt meter? The wiring for an ammeter is not large enough for a 100 amp alternator.

 

[cecho]

Re: Bad alternator.

Thanks! It's only got a volt meter.

 

[Don S]

Re: Bad alternator.

Then it's been changed, because they all wiring diagrams for pre BIA wiring, had ammeters. I doubt your old wiring will support a 110A alternator if the ammeter was bypassed at the dash by just hooking wires together. Look at the wiring at the helm on on the engine, and make sure the large red wire is not a red with white stripe.
Hate to see you end up with a wiring fire.

 

[cecho]

Re: Bad alternator.

The wiring at the helm looks stock and very well done. It has stock labels, a few harness and quick disconnects. The main power wire to the helm comes directly from the main off/1/both/2 switch and is larger than the wire coming off the output of the current alternator. I do not know what size it is in AWG, but I'd guess it's 4 or 6 AWG.

I'm going to have to trace the wiring from the alternator, but it looks like it's going to the same switch.

 

[wrench 3]

Re: Bad alternator.

The 10si should have a boss on the rear housing with a threaded hole in it for a ground. But don't use a bolt any longer than 1/2" or you will damage the rectifier.