LPG Generator - Electric Motor Drive

[NB Willawaw]

A boating friend of mine wants to build an inland waterways cruiser here in the UK. He wants to have a generator running off LPG (we need to find a genset that does that, provides 230V AC out and can be water cooled using a keel cooler), have that charging a big bank of traction batteries using a suitable charger and an electric motor to drive a single shaft.
We have been looking at the Lynch motor for the latter.

What we need help with is:

1. Sourcing a suitable LPG Genset - believe Onan make one for RV's but its air cooled and 120VAC out.

2. Estimating how big a motor we need to push the boat - we only need 4-6mph and the boat is 57ft x 6'10" beam.
We know what size of diesel inboard will do the trick - how do we calculate the motor size ??

The hull is being built first quarter 2006 and then the fit-out begins.

All constructive advice welcome.

[FAST FRED]

Honda makes a nice 6kw water cooled RV propane unit that might be avilable with British electric , rather than the US version.

Try the RV dealer , about $2500US

FAST FRED