Good morning,
Yesterday I removed the thermostat cover on top of the exhaust manifold to
replace the thermostat which I suspected was bad. I have a yanmar service
manual which has detailed drawings of the exhaust manifold on this sea water
cooled engine. To my surprise when I removed the cover there were TWO
thermostats installed for and aft on starboard side of the exhaust manifold
ports. The Yanmar service manual shows only ONE, in the forward port.
Since I only had one new thermostat I installed it in the forward port on
manifold, cleaned up the other from corrosion and put it back where it was.
The second port is machined to accept a thermostat.
If you have a yanmar service manual, pictures of this on page 7-A-2 showing one
thermostat.
Since these two ports are connected internally and water can flow through both
I am thinking that this is a safety factor. If one fails the other still may
open and allow cooling water to engine.
Any thoughts if this second thermostats belongs there? I have been running
this engine with it in place for 7 years and I suspect prior owner did as well
for a time.
Bill Walker
Evening Star
CnC 36
Pentwater, Mi
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