How to Identify a Marine vs. Auto Alternator?

[Unknown]

Recently a boat blew up near us that apparently had automotive (non ignition protected) alternators in it. That got me thinking - I bought my boat last year so I don't know for sure what type of alternators it is equipped with (I didn't put them in). I just took for granted they were marine since the boat was serviced by a reputable marine outfit. But now, being paranoid like everyone else who saw what happened to the other vessel, now I want to be sure I have marine ones in the boat...

The authorities obviously had some way to determine the type of alternators on that stricken boat. So my question is, how do I inspect mine to see what I've got??????

 

[stmbtwle]

A marine alternator (or one that has been converted) will have flame screens in it; you should be able to see them through the cooling vents. Might be other differences as well.

 

[Al_Prisco]

Pete, Like Willie said, there will be screens located on the cooling vents. Also the alternator in many cases will be painted and regulators and wirers will be sealed. On the newer units there will also be a rating sticker to show it meets marine standards.

 

[pdecat]

yes flame arrestor screens.
It is interesting to me that they dont stop the fire they just limit it to a small volume and prevent spreading outside of the alternator.

 

[PascalG]

it's like a flame arrestor on a carb engine... i've never really understood how that can allow the air to pass but not a flame.

so in theory, you would have fumes inside an alternator but they will burn off with no damage and it will not spread to the fumes outside ??

 

[pdecat]

Exactly, I think it works on the quench idea. The flame front is cooled quickly below the flash point. There must be some hole size rules but I haven’t seen them.

 

[SilverBullet]

The screen works the same way as a flame arrester on the carb and the screen in your fuel tank air vent. Hold some metal screen material over a burning candle to see the effect.