The Mastervolt GPX-5 is much more than a generator
. It's a whole hybrid drive system. Do you want to convert your drive or do you simply want to generate AC power?
If you want to generate AC power, then my advice to you -- with the usual disclaimers that it is my subjective opinion, YMMV, etc. -- is to strictly follow KISS.
A generator set is one of those things which should be as simple and reliable as possible. Gensets are one of the most troublesome items of equipment
on board, so avoid the ones which are delicate, overstressed or overcomplicated.
The usual solution is to buy a heavy duty low RPM
for 50hz power) genset like a Kohler, Onan (Perkins), or Northern Lights
. I have a 6.5kW Kohler with a 1,000cc three-cylinder Yanmar
and love it. It is quiet and the quality of the sound is also pleasant -- a low loping murmer which doesn't disturb anyone. This type of genset is supposed to be good for 10,000+ hours -- for practically continuous duty -- and is extremely simple.
The problem for you is that this type of genset is heavy, and you have a smallish catamaran
which will likely tolerate neither the volume nor the weight of something like that. You might be forced by these constraints to go with a Fischer-Panda, but I would advise you to avoid that if at all possible. These are complicated, poorly engineered, and notoriously unreliable, but -- they are the most compact and lightest units you will probably find.
Maybe you can get by with a high RPM (3,000 RPM) Onan or something like that.
One very important point -- don't oversize the genset. Don't size it for startup loads of your air conditioning
-- you can deal with those with the Power Assist feature of a Victron inverter/charger or similar functions of other similar inverter/chargers. Two reasons -- the genset will be happier if you can keep it loaded up to 40% -- 50% of capacity most of the time, and a smaller capacity genset will be lighter and less voluminous, which will be very important installing in something like your boat.