Alternator Problem?

[dbull75]

99 / 4.3 - 190 Mercruiser Alpha

I am having problems with the battery keeping a charge and I think the alternator is the issue. I have to charge the boat overnight before I take it out or it will not crank. I normally take it out every weekend since I got it in July. Any one know if there is an easy way to get to the alternator? From the way it looks, I would have to take out the power steering first in order to get to it. I was going to try and take the back seat wall/board but that does not seem like it will be as easy as I first thought. Any ideas?

 

[Don S]

Re: Alternator Problem?

It may be you have a bad battery, not a bad alternator. Start the engine (on muffs) and run it up to about 1500 rpm, then use a VOM to test the votage at the battery. If you see ~ 14 volts, the alternator is working. Make sure the belts are tight also.

If that's good, get the battery load tested.

 

[wire2]

Re: Alternator Problem?

First establish if the alternator is defective. Place a voltmeter on the battery, observe the volts, then start engine (in the water or with muffs). Does volts rise? If not, check volts at alternator output post. (larger wire, usually red) Still low? Check volts to alt. field, (2 smaller wires to a plug, may be purple & orange) Low or 0? May be a wiring problem or defective regulator, if it has a remote one.

 

[dbull75]

Re: Alternator Problem?

The guy told me the battery was brand new, but I will check just to make sure.

I will not be able to check volts at alternator output post due to not being able to get to it. Thanks for the help, I will try that when I get a chance.

 

[wire2]

Re: Alternator Problem?

As Don mentioned, make sure belt is tight.
An alternator trying to charge a low battery can draw up to 5 HP of energy from the crank.