Alternators

[DH]

What is the alternator of choice now? I have the old universal, 10 hp. Mine doesn't seem to be putting out enough juice. Have two gell batteries two years old. Everything was ok last year, but my self steering is cutting off because of "low battery". I haven't done the trouble shooting yet. Plan to tormorrow. But I suspect the alternator as well as the battery charger. Both are about twenty years old.

PS, a helpful guest did swithch the battery switch from Battery one to both while the engine was running. So if it is a blown (anode/diode or whatever you call it) would I just take the alternator to an automobile repair shop, or is that a repair that is relatively easy to do.