The exsisting hot water heater is rusting apart.I have searched the archives and found there are two round hot water heaters. Raritan and Super stor. They are both priced about the same at defender.com and have about the same dimensions. I know Peggy likes the Raritan better [from the archives} and that weighs heavily in their favor. I am looking for advice on which one hooks up the least amount of difficulty as neither is an exact replacement. Any advice on how to do it is appreciated. The boat is an 1986 Catalina 27 with the m-18 engine and an existing 6 gallon {rusted} hot water tank w/exchanger. Thanks, Jack