MD11c problems

[dah]

I have a Centaur, with a Volvo MD11c inboard. The engine starts well and is generally reliable.Recently I have had water flow problems when under way.
Having started and preparing to sail, the engine will run quite happily.However, after slipping the mooring and motoring out of the estuary, problems start.
After several minutes under load the water flow stops, the temp gauge rises from green to red, at which point the flow resumes and the needle goes back to green.
After several minutes the procedure repeats itself, ad infinitum. Water stops, needle rises, flow restarts, needle sinks, etc, etc, etc.
I have had the manifold off and cleaned all the passages. The exhaust elbow has also been pressure cleaned. All to no avail. However, when I remove the thermostat, also new, The water flow is completely normal and the engine runs quite happily. Therefore a blockage would not appear to be the problem, but somehow linked to the thermostat in situ.
Any help/advice please as I would obviously rather run the engine at the proper operating temp when under power.

 

[PaulJ]

It certainly sounds like a sticking thermostat. Put it in a saucepan of water on the stove and watch what happens - it should open smoothly a bit before the water boils...... if it doesn't then get a new one - in fact since you will have had all the hassle of getting it out it is probably worth replacing it anyway as they don't last for ever and don't cost much.

 

[Jcorstorphine]

may sound daft but is the thermostat in the right way up?

john c

 

[Guest]

Take the thermoustat out and have a very very close look at the water hole in the casting. It's hard to see down there in the gloom but on my engine the water way has closed to about one eighth of an inch. Cleaned out it should be about half an inch diameter. Once this had been opened out my overheating problem cleared however, the casting then needed welding to stop a drip as the casting had eroded further than the thermoustat cover could seal.

Good luck

Cheers

John Dillon