OMC Cobra 5.0 Alternator Problems

[urbantux]

I have an OMC Cobra 5.0 FORD motor in my boat, it is from '93 I think. Last time out I noticed the Volt meter wasn't registering. Further inspection found the alternator belt had broke. I replaced the belt but the volt meter is still showing nothing.

Looking at the wiring there is a small snap in connector on the bottom of the alternator with a Red and White wire coming out, the red wire is connected to a purple wire and the white wire to nothing.

The alternator is not OEM, it looks like the previous owner put a NAPA alternator on there. So this raises two questions:

1.) Should the white wire be connected to something? If not is the alternator just bad?

2.) Is a NAPA alternator even the right thing to have on there in the first place?

Any help would be awesome.

 

[bruceb58]

Re: OMC Cobra 5.0 Alternator Problems

A NAPA alternator is fine as long as its a marine alternator. Have you checked the voltage of the alternator output with a handheld voltmeter?

 

[urbantux]

Re: OMC Cobra 5.0 Alternator Problems

A NAPA alternator is fine as long as its a marine alternator. Have you checked the voltage of the alternator output with a handheld voltmeter?

I don't have a voltmeter, and I wouldn't be sure which connections to test. It just doesn't seem right to have a dangling wire. I tried connecting that white wire to the purple cable and it would read volts but turning the ignition to off doesn't kill the engine.

 

[bruceb58]

Re: OMC Cobra 5.0 Alternator Problems

Sometimes, the extra wire is used for an idiot light. I would definitely check the serial number of that alternator with a Napa store to make sure you have a marine alternator in there.

Just check the battery voltage while the engine is running. Pick up a cheap voltmeter at Harbor Freight or a store like that. If the voltage is between 13.6 and 14.2 or so, your alternator is working.

 

[urbantux]

Re: OMC Cobra 5.0 Alternator Problems

The way it is wire the alternator isn't working, the voltmeter on the boat registers nothing and removing the positive battery cable with engine running results in the engine no longer running.

 

[bruceb58]

Re: OMC Cobra 5.0 Alternator Problems

Never remove the battery cable with the engine running. That will kill your alternator. Maybe that is why it doesn't work if you have been doing that.

Like I said before, that white wire is probably for an idiot light. The other wire is going to be the excitor wire. It needs to have voltage to it when the ignition is on.

If the voltmeter on the boat doesn't even register battery voltage, it either is not hooked up anymore or broken. You need to ignore it for now. Buy a handheld voltmeter.

 

[urbantux]

Re: OMC Cobra 5.0 Alternator Problems

I have a friend coming by this evening with a voltmeter. I talked to the previous owner and he isn't sure it is even a marine alternator so I went ahead and put a replacement MARINE alternator on order.

Hope it works out, I guess I will have to wait and see tomorrow.