Yanmar Coolant ports.

[Captain Bill]

Does anyone happen to know the thread size for the auxillary coolant ports on a Yanmar 3JH3 series. I want to tap the coolant to use a hydronic heating unit. These ports are on/near the thermostat housing and on my port engine are used for the water heater. I suspect the plugs currently in the ports are probably metric, but could be npt. I have thread guages here at home, but I would like to save myself a 180 mile trip to my boat and actually have the correct parts when I take the heater down to install it. Also if they are metric does anyone know where to buy metric hose adapters.

[never monday]

should be 1/2 or 3/8 NPT. It is possible one is a straight thread metric.

[Captain Bill]

Thanks, I didn't have a thread guage with me last time I was there, but I measured the outside diameter and it was 5/8 of an inch which would be correct for 3/8 NPT, but I was afraid that it might be 15mm. I'll get a pair of 3/8 npt to hose adapters.