Alternator output at 45V??

My alternator is pushing 45 volts which is far over the expected 14 volts. This suggests that my voltage regulator is shot. I’m trying to decide what to do... replace the voltage regulator? Or get a new alternator? I’m way over budget so I would rather not spend the extra money if I don’t have to, but I read that these alternators are built so that any internal sparks don’t reach the surrounding air so not to ignite fumes within the doghouse. With it being an old alternator I’m thinking “what if this thing is producing exposed sparks within?” What’s you guys’ opinion on this?

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Which ever route you go, you need a marine alternator or marine components.

My question is, where did you measure that 45V? At the battery or right at the alternator output? Right at the alt might indicate an open field situation due to a bad cable.

Call around and find a local starter/alternator shop...they can bench test it and typically won't charge anything to do so. From there you can determine what part(s) are bad of at all with the alternator and determine next steps. You can replace it for around what it would cost to fill the boat with gas though.

Just for reference, I've got an older BMW 740 that was having alternator issues...it was pushing between 16-18v spikes which were essentially boiling the battery acid. The whole car wreaked of rotten eggs/sulfur. If yours is throwing out 45v you may want to double check everything back to your Batts.

Also, not sure you meant to start this thread in the classifieds...maybe a moderator can tow it to the service area?

^ done and a bump

Second the local automotive electrical shop. Took one in once and they rebuilt it maintaining marine protections. Actually, they increased the output too. They also had rebuilt marine alternators in stock in various sizes and makes.

Thanks for all of the info! Ive got 2 new batteries in the boat and haven’t connected the alternator since they’ve been in, so I should be good there.

Okay so sounds like I need to start with taking it in. I went ahead and replaced the regulator because every thread that I read suggested that to be the culprit.... BUT STILL 45-50v! I tested other connections on the alternator and found a red wire that is pushing 14.3V which sounds perfect, but I’m skeptical because that’s not where the charging lead was connected originally.

Next step: take everyone’s advice, take it in, and ask a pro.


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