I use a Xtreme heater, 450w model on my Bayliner 2455. Seems to work good. I don’t keep my boat in the water and I use a small electric cabin heater set to the lowest setting in the cabin. This keeps the cabin in the 50’s. I have all the cabinets opened and seat cushions up so the heat can get everywhere. Xtreme Heater Top View I really like the idea of taking the boat out on the occasional higher temp days we get in the Washington DC area I installed an Xtreme heater in my bilge last year and they work great!