Voltage regulator
Mike,I would check with a local starter/alternator shop. Or even a major auto supply store. Although most of the auto supply guys don't know squat, about what they sell, you might get lucky. Most of those things are made by someone else for Westerbeke, Yanmar etc. More than likely there are plenty of others that will work. Basically, all most of them do is provide the exciter voltage for the alternator depending on battery voltage. The older Chrysler regulators, made before built in regulators, were very good, and reliable. Small enough not to cause a mounting problem. And there is no reason you can't use a auto regulator on a boat.