My mate in the Creek has a 38 foot Bavaria and told me yesterday that his alternator runs very
hot, 'red hot' he reckoned. Is this a worry ?, is it a symptom of something mismatched ?. I'd like
to pass on any advice to him.

Bit of googling....

The diodes in your alternator are shorted out and holding the charge you are making when the engine is running, this causes the heat because they are unable to discharge the energy they are storing.

If it were mine i would replace.

A? Uncle bob says.
There is the added risk of engine room fire?

Thanks guys....obviously he's going to have to take it off and get it checked out. Thanks for the response.

Datawiz said..

samsturdy said..
My mate in the Creek has a 38 foot Bavaria and told me yesterday that his alternator runs very
hot, 'red hot' he reckoned. Is this a worry ?, is it a symptom of something mismatched ?. I'd like
to pass on any advice to him.

Sam, very high likelihood the alternator has at least one diode shorted. The right auto electrical specialist will probably be able to replace the faulty diode(s).
It could be a fire risk running in this condition.
This failure can be caused by switching the Battery selector switch whilst the engine is running, or any other action that results in the alternator not being connected to a battery when running.

regards,
allan

Thanks Allan. I've just contacted him to say the consensus was a diode failure and could cause a fire, so
he's doing something about it pronto. It's a lovely boat and I would hate for a fire to happen. Thanks all.

Whoops for the hi jack... I've an old school book that describes a way of manually manipulating the field on an Alternator to gain continued max amps...... Suggested way to tell if your working the alternator to hard was " if you can't hold your hand on the alt for more than 30 seconds back off engine rps or ohms "
its allways good to have gear checked but how hot is too hot for an alternator???

Just checked sams op. Yep red hot would be too hot !