im considering buying a boat which is converted to lpg what problems can occur with insurance companies re same

There is a risk of gas leaks building up in the bilges causing an explosion. Petrol can do the same, but doesn't come in a pressurised system. You need to be sure the system was competently converted and has all the shut-off valves, vents &c. Get a proper marine surveyor to look at it, and get insurance quote before purchase

I am never happy with gas on a boat and I wouldn't have Lpg as I can't see much advantage over diesel unless it is a real big guzzler. You must ask an insurance company

Gawd, I wouldn't have lpg on board. Floating bomb! I know petrol's as bad, but at least you can see it accumulating in the bilge. Diesel for me.