Another MD2020 overheating...

[Ammonite]

The opposite is the case as the prop loads the engine more. Would be lucky to get to 3000rpm tied up. Anyway it really should not make any difference as the thermostat regulates the engine temperature assuming there is good flow of seawater which seems to be the case.

If that is true I stand corrected although it doesn't change the basic overheating scenario I was describing.

 

[Beneteau381]

simply speaking, tiedup, you dont get the same flow over the prop and it is inefficient. Corrected, Tranona got it.

 

[Ammonite]

simply speaking, tiedup, you dont get the same flow over the prop and it is inefficient. Corrected, Tranona got it.

I suspect my confusion stems from having an Autoprop which will hapilly allow the engine to spin up to 3600rpm in gear alongside, almost as easily as if it was in neutral, but will struggle to reach 3000rpm underway. I appreciate that is very different from a fixed prop as it automatically re-pitches as the boat picks up speed

 

[Birdseye]

I dont see the thermostat having intermittent failures simply because of the design of them. Its the sort of component that either works OK or not.

The overheat alarm should trigger before the engine spits out its coolant through boiling provided the filler cap works and boiling is at the higher temperature that the filler cap is there to ensure. So my first step if it was my enigine and I didnt have a thermometer to check would be to replace filler cap and temp sensor. Better still get an infra red thermometer and measure the engine temperature after a good long run.

Have you re-torqued the head bolts after the initial run?

 

[Bilgediver]

I will replace the filler cap and thermostat as a precaution.

I would suggest that you also put an expansion bottle at the e d of the plastic tube. It does not need to be pressurised but make sure the tub goes to the bottom of the expansion vessel and make sure you have a radiator cap which allows reverse flow so water is drawn back to the engine on cooling.

You could buy a proper pressurised expansion vessel however you would the. Need to move the radiator cap on the engine to the expansi9n vessel and fit a non valved cap on the engine.

It is bad practice not to run the heat out of a diesel before stopping .This can start by speed reduction before arrival at the marina and then let the engine idle for a few minutes as things are sorted on deck post arrival.

 

[MikeBz]

Have you re-torqued the head bolts after the initial run?

That's on my job list to do next, along with checking the valve clearances.

I would suggest that you also put an expansion bottle at the e d of the plastic tube. It does not need to be pressurised but make sure the tub goes to the bottom of the expansion vessel and make sure you have a radiator cap which allows reverse flow so water is drawn back to the engine on cooling.

You could buy a proper pressurised expansion vessel however you would the. Need to move the radiator cap on the engine to the expansi9n vessel and fit a non valved cap on the engine.

It is bad practice not to run the heat out of a diesel before stopping .This can start by speed reduction before arrival at the marina and then let the engine idle for a few minutes as things are sorted on deck post arrival.

I temporarily cable-tied a 1-litre water bottle in place with the overflow into it after the incident, I'll make that something more permanent. The prices for all the parts to fit a genuine VP expansion tank are hilarious - Volvo Penta Shop.

I do always slow down some time before stopping, and idle for a minute or two after that (legacy of having run/raced cars on circuits!) - I still call it a 'cool-down lap'.

 

[Bilgediver]

You should be able to get an expansion bottle from an Auto parts place or breakers yard.

 

[DownWest]

I had a temp overheating situation (likely) caused by a plastic bag. It then continued to over heat even though the flow was OK. Turned out the thermostat cover's tube outlet to the expansion tank was blocked by crud. One it had overheated, it could not clear the air from the system. Reemed it out and problem sorted. This was the 3 pot Perkins/VP.

 

[tsekul]

I posted about this a couple of months ago.

We haven't had an issue since and have concluded that there was a temporary blockage of the sail drive raw water inlet. we have motored further with higher revs for longer periods.

I would say be vigilant and monitor it if it happens again then cross that bridge