Kevin-yours is an interesting point. In a lot of years boating, I actually have never heard anyone mention the generator end of the genset. I certainly have never given it a thought. All mention is of the engine end. I always just sort of assumed that the generator end came from the maker of the genset, not from a third party manufacturer. Thanks for enlightening me!
People do not realize that the generator business is really putting together parts and putting your name on the generator.
Not all manufacturers are like this of course but thats the way it is for the most part.
A generator is nothing more than a prime mover (engine) coupled to a generator end, and add a control panel. Choose your brands.
The interface between the generator and the engine is all using standard SAE sized equipment now days. The engine has a SAE bellhousing and flywheel, and the generator end has the matching bellhousing and flex plates that bolt to the flywheel.
This trend at least in smaller generators started with the first EPA regulations years ago. Remember the ONAN MDJ series of generators. That was a ONAN engine with a tapered crank shaft fitted to an ONAN YD alternator.
The EPA caused ONAN to rethink wether they wanted to be in the engine business and they dropped the engine lines and went with bulk engine suppliers. Then they also dropped the generator end manufacturing side and bought generator ends.
Later Onan units were Kubota powered if memory serves correctly, and they were running Stamford Newage generator ends.
Northern Lights uses Kubota engines and Marathon generator ends in their small units. For awhile they used a brand out of Japan that was pretty good.
Control panels can come from several sources. A company called Deep Sea Electronics PLC seems to dominate that market.
So, if you want to build your own generator...
Buy a engine
govern it at 1800 rpm (or 1200 if you want a really long lasting unit)
Buy a generator end
Buy a control panel
Walla, Trawler Forum brand generators