overcharging and boat won't shut off

[thundercat 9]

Hey guys,

I think I have a grounding "gremlin". At first, the volt meter on my dash started reading between 14 and 16 volts so I took my meter and checked the battery and sure enough, it was between 14 and 16 volts depending on the RPM of the engine. I put a new alternator in and still no change, the only difference now is the motor won't shut off with the key, but if I disconnect the (engine)Pink wire from the alternator white wire, the engine stops...The pink wire I'm talking about splits from one to two (one goes to the plug in wiring harness and the other goes to the coil).

Any ideas???:redface:

 

[wire2]

Re: overcharging and boat won't shut off

The ignition is getting 12v from somewhere other than the key. Is the new alternator the same as the old one? Have you changed a wire connection?

 

[Don S]

Re: overcharging and boat won't shut off

It would sure help to know what you are working on.

 

[Smacken]

Re: overcharging and boat won't shut off

Wow, PEI? Pretty well the only reason I'm responding, But i will tell you that I had installed a new altenater on my 3.0 Merc a few weeks ago that was pushing 18v into my battery/coil. It was bought locally here, and deemed defective. Not sure if that is any help to you.

 

[thundercat 9]

Re: overcharging and boat won't shut off

Yes, it's the same alternator(Positive bolt/nut terminal on the back, bolt into the housing for the ground, and a 2 wire push in type pigtail) The only thing I changed is I had to bypass the pink wire in the harness( the one that comes from the 2 wire connector on the alternator and goes to the wiring harness plug and the positive side of the coil) because when this problem first happened, it heated up that wire and melted it a little. I cut the pink wire just before the section that splits into 2 wires(one going to the wiring harness plug and the other going to the positive side of the coil). The wire I used to replace it is about twice the pink wires size, would resistance make a difference?

As for getting 12 volts from somewhere else, could a bad key switch cause this?

Thanks

 

[thundercat 9]

Re: overcharging and boat won't shut off

Hey Smaken, thanks for the reply.

I bought a rebuild last summer and it might of had about 15 hours on it then this happened. I took it back to the place I bought it from and they replaced it with another one.(What are the odds of it also being defective?)

It is a 1988 mercruiser 350/260 hp with the thunderbolt IV ignition.

 

[Smacken]

Re: overcharging and boat won't shut off

What are the odds of it also being defective?)

Pretty good if we both bought them from the same supplier! Did you check the voltage coming out of it running? Mine came from a supplier in Ch'town and I won't mention them as I don't want to appear like I wasn't happy, but they fixed it right up and replaced it. S*#t happens.

 

[thundercat 9]

Re: overcharging and boat won't shut off

Actually, I'm in New Brunswick now. The alternator is a Dixie Electric Ltd. alternator. I did my testing last night and at the battery, it was charging a little high. I've found some info on testing the alternator while its on the motor so I'll give that a try and see if the regulator is good or bad.

 

[Don S]

Re: overcharging and boat won't shut off

I think the first thing you need to do is ID the wires and alternator to make sure they are like the OEM setup. Since OEM doesn't have a pink wire going to the alternator, you may have to trace it back and see what color it was before it faded.
Here is the wiring diagram for your engine. I left it as a .pdf file so you could blow it up and make it easier to read.
If you melted a wire along the line, it's hard to say what all is wrong or where. But I doubt it's a couple of bad alternators. It's possible your wiring is frying the alternators.

http://www.4shared.com/document/0TSzZhV3/Wiring_diagram_88_57.html

 

[thundercat 9]

Re: overcharging and boat won't shut off

hey Don,

Thanks for the reply. I looked at the wiring diagram and it's not exactly like mine, I do agree that the pink wire I talk about could be a faded red, but I peeled back the coating on the harness and the wire still looks pinkish.Also, regardless of the color, the wire off of my alternator splits and goes to both the wiring harness plug and the positive side of the coil, which none of the wires on the schematic do.
All the wiring harness looks original(no mickey mousing).

I guess it could be a faded purple....I think I have my work cut out for me...

Thanks

 

[Don S]

Re: overcharging and boat won't shut off

I looked at the wiring diagram and it's not exactly like mine,

What's different? All the alternators and wiring for the alt. was the same on all the 5.7 engines of that era.

 

[thundercat 9]

Re: overcharging and boat won't shut off

Let's say that my wire from the alternator is purple,like the one in the schematic,the one in the schematic splits and goes to the coil and choke, mine splits and goes to the coil and wiring harness plug. I have a mechanical choke on my motor. I don't know if that makes a difference, I'm just saying...

 

[Don S]

Re: overcharging and boat won't shut off

Here is a link to the service manual for your engine, there is a section for the charging system. Might want to do some testing on the alternator to see if that is your problem, also check out the different wiring diagrams.

 

[thundercat 9]

Re: overcharging and boat won't shut off

thanks Don, just another quick question, I've been browsing the forum and I see people talking about a "resistor wire". Do I have one on my set up?

Thanks

Jeff

 

[Don S]

Re: overcharging and boat won't shut off

Nope, the resistor wire is for points ignitions only.