Your hint with the little pipe in the manifold would be an explanation. The manifold was used in salt water
but in a fresh water cooling
system and was pressure tested. The thermostat is the one that was in before and has the little plate at the end but no hole at 1200.
However, I do have the warm water heater
heated by the engine
and this adds about 2cm between the manifold and the thermostat housing for the outlet. So if the pipe that was in the manifold was not made for that it is likely that the thermostat is not able to bridge the whole gap. This is easily measured and tested next time I will be at the boat
(which is 400km away and still have a working life).
I guess that the coolant
is not properly routed through the cylinders when this pipe is open and this would explain as well the temperature diff between the thermostat housing and the cylinder heads.
What I am still puzzled about is why it did perfectly work
for the first two hours before it started to degrade and it feels as it would degrade even more every time I used the engine
(under load). The last time made it barely out of the marina (about 1.3 nm).
It would mean as well that removing the thermostat in emergency
situations (broken and no spare on board) would not help at all as the is nothing that would close that little pipe. True?
Regarding the circulation pump
: the two ones that I have were both rebuilt recently (the one installed about 3y ago) with ceramic seals
, a new shaft and a brass pump wheel
. So it not very likely that this pump failed.
Your tech explanation writing skills are just fine :-)