engine coolant

Hey coolant experts... Soon after we purchased our boat in 2020, I dove into the list of chores identified from the survey. One of these was replacing the hydronic cabin heater, which was badly corroded and nonfunctional. I isolated that loop at the engine (valve), removed the old heater, and...

Good morning all, I'm hoping for confirmation that my Yanmar 3jh3e freshwater/coolant pump actually has two parallel loops/sides: 1) an engine coolant side, and 2) a "domestic hot water" side. (I completely understand there is a RAW water loop, with it's own pump, that goes to the heat...

Hi, I'm going to replace my water heater. The photo shows the engine coolant lines that go to and return from the water heater. What is the circled valve for (I assume it's a valve), and will it help me when I replace the heater? Engine is a fresh water cooled Yanmar 3JH2E in a 1994...