I have a 5KW Sea Power unit on my 1983 42' Grand Banks and love it. Not only does it supply aux ac power when my generator is down, but it is a pleasure to have constant ac power when cruising, to run fridge, freezer, ice maker and space heater if needed. It can also handle air conditioning and is very clean power which is always acceptable to all my computer systems on board. By the way, this unit is a constant hertz, constant voltage at all rpm's. Lower RPM's yield less KW.
The original people involved with this product are based out of Texas and go bu the name Mobile Power. I guess there is more of a land market for these units.
I highly recomend this product and have found Bill Chambers to always be a gentlman in all dealings with his company.
Sea Power / Mobile Power
Feel free to contact me with any questions: firstname.lastname@example.org