Learning the HARD way...
Join Date: Jan 2007
Location: Boston / Ft Myers Area
Thanked 278 Times in 273 Posts
Rep Power: 13
Dave, I am VERY familiar with how the water heater is plumbed on an O'day 35 with an M25. The factory did this poorly, by plumbing it between the Heat Exchanger and the Exhaust Manifold. IIRC, the HX uses 5/8 hose, and the WH uses 1/2 inch. While you can get a fitting which allows you to connect the two, a better way for the engine, and the WH is to connect the HX output directly to the exhaust manifold. Connect the WH to the 3/8 nipple for the thermostat bypass (at the front of the engine). The engine temperature will be more consistent, you'll get hot water faster, and of there is a leak, it will be in a smaller diameter hose.