I have a 3QM30 (Raw Water Cooled) Yanmar which has 2 thermostats installed, but the local Yanmar mechanic and service manual drawings both indicate I should only have one installed. The housing is built to take 2 thermostats (in parallel) and if I remove one, then the raw water will bypass the remaining thermostat rendering it ineffective. The motor runs fine (temperature wise) with 2 thermostats installed.

Have any of you come across this " 2 Thermostat" conundrum previously. I googled it and found a few references to the same issue but nothing official.

My thoughts are that I will be using 2 thermostats and dare I say, "Yanmar may not have delved deep enough into my request for information and ......." The local mechanism did his best to find out, but he is also relying on Yanmar to give him the correct information as well.

(The thermostat housing is built into the exhaust manifold and is different from the 2QM20.)

Cheers