First thing you need to do is determine what type of mounting configuration you have and then find an alternator (of whatever brand) that will fit that configuration. There are many different manufacturers of suitable marine
sells Balmars but they have a reasonably good and easy to understand guide to selecting an alternator:
Selecting an Alternator | West Marine
Many companies provide select alternators for select engines. This is primarily to help owners to get one that will fit, but you can do this yourself. Also specific engines usually come with a specific wiring
harness that is compatible with their alternators, but there are a huge number of different harnesses so many of these selections are designed to be plug
and play with these harnesses. If you will be using an external regulator
you will have to modify this any way. Also, your diesel
does not have to have an alternator that is rated for gasoline engines, but you could use one of those if it otherwise meets your needs.
I found a link to Electromaxx but am not recommending it specifically. There are others, including Delco, Hitachi, Prestolite, Denso, Leece-Neville and other marine
type alternators. And just because an alternator is sold as for a particular engine
model xyz) that does not mean it would not work on your engine
. But you do need to understand how you would wire it in. I don't know if you have a need for a "tach" or "AC" output or it has to be specific to your gauges. You will have to sort that out as well - different gauge, or different sender,.... But you may not have that issue at all.
Electromaax High Output Marine Alternators