I installed a pair on my 36 Albin Trawler last season. Easy to install, not so cheap, sharp as hell. Haven't been in a situation where I needed them yet, but it's bound to happen at some time.
Water Heaters
I installed a Quick Nautic Boiler water heater in my last boat. Stainless tank, urethane insulation, high efficiency heat exchanger. This was a nice unit for a reasonable price. It's worth taking a look to see if it meets your needs.