Yanmar 3GM(F) Water Heater Performance

[kloudie1]

ZDS, your manual is better than mine since it shows both configurations.. Good Deal.. I think you'll be happy once ya move the water heater out connection. You probably could carefully drill and tap a hole in the old pump housing/bracket (making it like the new one) to put both connections below the thermostat.. but you'd want to be really careful doing that.. It looks like you could do it in situ and use magnets to clean up afterwards?? Just thinking out loud.. Probably unnecessary.. I'd thought that someone had inadvertently reversed the positions of the switch and the WH outlet on your engine, but the book clearly shows that is where they intended it to be hooked up.. I dunno.. Happy Heating!

 

[zds]

Reversing the temp sensor and the above-the-thermostat coolant line did the trick - hot coolant running through the tubes in less than 10 minutes at a fast idle!

I've ordered a 3/8 PT tee-fitting so that I'll be able to keep the coolant sensor in the bypass flow, and a plug for the now-unused hole above the thermostat. Maybe one day I'll go so far as actually putting a gauge sender in...

Now I just have to figure out how long it takes to get hot water from that hot coolant (it's something more than ten minutes...)

 

[Joseph Shirley]

They may be plumbed backwards. I don't have my engine books in front of me as I write this and I actually have a 3HM35F which is extreme,y similar but slightly bigger. Yanmar thermostats are built with an internal bypass so there is some water circulating even when it is closed. It seems to me that the supply should come from the port side of the thermostat so that the pump will move significant water through your heater even when the thermostat is closed and the supply to your tank should be the lower of the two hoses connected so the hot water enters at the bottom. You can also check yout thermostat bu taking it out and watch it in a pan of heating water. use a thermometer graduated to more than two fifty and determine at what temperature the thermostat pops open. No cost involved.

Have fun

Joe S

 

[kloudie1]

ZDS, Great news.. careful with making too much of a "tree" with extensions off the one port. The vibrations of our little three bangers can cause a fatigue crack at the engine if there is too much stuff hanging off one nipple.. Good to know that ya have fast hot water now !

 

[mark_swart]

My H34 was very quick to heat water, after I first bought it. The boat had been out of the water for about 6 months, with all water drained out of the fresh water. Now it is slow and sounds alot like ZDS's. It's hit or miss as to when or how hot it gets.
I think maybe there is an obstruction. I would think maybe you could reverse the lines to backflow and free it up, but the gunk would still be in there. What about disconnecting both ends on the engine, then rigging a garden hose in reverse cycle just to try and free up anything in the heater coil?
Anyone tried that?