Engine proper temperature before shutting down

[Zing]

In the absence of a coolant temperature gauge, how do I ensure that the engine has reached normal temperature before shutting down and hoist the sails? Is there a rule of thump? I will warm up the engine by starting, leaving the marina and slowly reaching cruising rpm (75-80% of full throttle) but then for how long do I need to run it at these rpm? Engine is a volvo penta d2-75 (turbo charged) if this matters?
Thanks

Fit a gauge to buy a cheap thermometer, or get an infrared one, useful for lots of things. I think the main problem if you regularly shut down before the oil has got hot is that you will not boil off any water in it and risk slowly corroding the engine. As you have a turbo, don’t forget to cool it off properly before shutting down to avoid carbonising the bearings.

 

[[159032]]

Trying to think what the consequence is of shutting down after 5 minutes. I would expect bores to be warm enough to avoid condensation of moisture in exhaust gases. Sulfur is so low now that sulfurous/sulfuric acids are almost negligible. A few other weak organic acids may be present but these mostly require high temperatures for generation. So overall I doubt there are any serious consequences in shutting down cool.

Quite. There are lots of mother's tales about old mechanical devices which are, at best, tenuous information of the time. The point about diesels in vehicles running and shutting down on short journeys is one. Diesels have always been know for longevity. No wonder. They don't rev much and are built for WW3 levels of stress.
I still know farmer types who never turn off their motor even, when they go for lunch. On the other hand, diesels which are hard to start have tended to be in small trucks which have had long hard lives. Just worn out and probably revved too much. They prefer running in a narrow rev band.

 

[Chris_Robb]

...........find the medical kit

I told you it was hot

 

[Skylark]

Re turbo engines. Oil thermal degradation leading to bearing damage was an issue with gasoline engine applications in the 1980s and from memory the Renault 5 was probably the worst example. The issue was solved by adding a water jacket to the bearing housing and plumbing it in such a way that a thermal siphon dissipated the heat after shutdown. Diesel engine exhausts temperatures were not high enough to cook the oil so never needed water cooled bearing housings. Water cooling of the turbine housing is to meet an engine bay surface temperature regulation.

Most turbo seals are labyrinth arrangement and one of the most difficult tests to pass is long duration idle. Not uncommon for them to leak after a long period of idle.

 

[Chris_Robb]

Re turbo engines. Oil thermal degradation leading to bearing damage was an issue with gasoline engine applications in the 1980s and from memory the Renault 5 was probably the worst example. The issue was solved by adding a water jacket to the bearing housing and plumbing it in such a way that a thermal siphon dissipated the heat after shutdown. Diesel engine exhausts temperatures were not high enough to cook the oil so never needed water cooled bearing housings. Water cooling of the turbine housing is to meet an engine bay surface temperature regulation.

Most turbo seals are labyrinth arrangement and one of the most difficult tests to pass is long duration idle. Not uncommon for them to leak after a long period of idle.

Interesting new view. I have always just applied logic..... In most cases when docking one does let the engine idle anyway....

 

[Skylark]

Interesting new view. I have always just applied logic..... In most cases when docking one does let the engine idle anyway....

There’s nothing new about my view, in fact I’m probably a bit out of date as I left the business more than 10 years ago. I worked with turbos as OE fitments to engine makers for 20 years.