View Full Version : Alternator

08-23-2004, 09:10 PM
Hey All,

Here are some issues - the panel voltmeter NEVER reads 12V, even when I know the alternator should be charging - when I put my digital voltmeter on the large orange wire on the alt. I get 12.67 with the engine running (even idealling up to 800 rpm). My battery reads about 12.2 at the terminals even with the boat running ...bear in mind this is after cranking on it for a while (yes, it takes a while for the ole motor to kick and start, but it DOES start) so I would think the alt. would be sending a bit more than 12.2 to top it back off?

I thought alternators put out around 14+ volts...? IS it time to have the alternator bench checked? Also, can you buy just a starter solenoid? The solenoid would click several times before engaging alot of the time so I took it apart and found the backside of one of the posts kind of pitted where it had been arcing and sparking, I merely turned this post 180 degrees so it presented a clean portion of the post to the contact point - seemed to work fine for about a week and now it just started doing it's clicking thing again - could this all be tied into some sort of low power deal caused by the alternator?

Sorry about the long schpeel...


08-23-2004, 09:45 PM
Bench testing the atlernator isn't a bad idea. If that tests OK, then I would be looking at the battery's ability to handle a heavy load. If OK, I would look at the battery cables and terminals for their condition, as well as the grounds on the motor. Including the starter bolts and mating surfaces, since this is where the starter ground is established in the first place. If these are dirty and/or corroded, the starter suffers due to the voltage drop(remember, P=IxE).

The solenoid should be available seperately and if it has burned contacts, it usually indicates problems with the voltage path.

Another thing I would check is if the timing is advanced too much and making it hard to crank the motor.

08-24-2004, 08:39 AM
Thank you Jim,

It seems my local yocal friends have talked me into a Pertronix electronic ignition (new coil as well) so when I do that install I'll have a go with the timing light....

Battery is new (I know, that doesn't necessarily mean it's GOOD), the terminals are all clean and shiny - oh here's one - after I wrote the post I went and started checking with the volt meter again and found 14 volts when I put my ground lead on the alternator tensioning bolt, EVERYWHERE else (engine block, etc.) the voltage measures the above mentioned 12.6... so this afternoon I'll go and loosen, clena and tighten everything back down - most things are pretty clean and not corrodey but who knows


08-24-2004, 08:41 AM
I agree with Jim, have the alternator tested first. It should be putting out at least 13.5 volts at 2 k rpm. And I cannot stress enough CABLES AND CONNECTIONS!, years ago I worked in the battery business and about 50% of the batteries replaced were not bad. This would indicate that by changing the battery people move aroud the termanials enough to clean them a bit then they work better. Don't stop there, clean all termanials and the starter mounted surface as Jim said.

If you are taking your alternator in for testing, I would also have them check the battery while you are there.

08-24-2004, 11:32 AM
I see from your profile you have an 89 w/454. I have an 88 with the 351 W so it is not quite the same. However I had a lot of problems this summer very similar to yours. The alternator was not (apparently) charging the battery very well and only reading around 12V. The battery was new.

My problem turned out to be two-fold. By all means, pull the alternator and take it to AutoZone, Pep Boys, etc and have it tested. However I would recommend you go ahead and take the starter as well. My alternator was tested marginal. As it was 16 year old I went ahead and replaced it. That helped some but starting was still very difficult and the voltage in the boat seemed low. Then I pulled the starter and had it tested. You could hear the bearings rattling as soon as they but it on the bench and gave it power. Got a new one and everything has been great since then.

Like most people on this board (it seems) I got my parts from Discount Inboard Marine. Fair prices (remember these must be marine components) and great service. Good luck.