Diesel engine warm up and cool down?

Stu Jackson · Apr 20, 2010

Don't warm it up.

Go out and run it.

Let it cool down before you turn it off. You only need to do this if your temperature swings and is elevated when you pull into your slip. Most diesels should run at pretty much the same operating temperature all day long. If it doesn't, check your HX, raw water pump, inlet seacock, and exhaust riser.

Maine Sail · Apr 20, 2010

What they probably meant was that short runs of a diesel engine, in and out of a harbor, do a ;ot to shorten the life. Short runs lead to built up internal condensation that is normally burned off after a long hard run. Starting the engine for fifteen minutes here and there is not generally very good for it..

firehoser75 · Apr 20, 2010

Hi Mike,
Stu is absolutely correct. Do not "warm up" a diesel. After starting you can leave your slip about as soon as you can cast off the lines. Motor slowly for a few minutes and then gradually bring the engine up to cruising RPM's. When coming back into the marina, you probably motor down at least one set of docks under reduced speed. After tying her up, let the engine idle for a couple of minutes to "cool down" and then "kill it". Assuming it isn't running very hot.
The biggest problem for sailboat diesels is the fact that most of us leave the slip and motor for less than 10-15 minutes and then raise sail. The engine never even reaches full temperature. We tend to do this repeatedly. Very hard on the engine. Diesels like to work!
Good luck,
Tom

Additional info is available on the thread "How Many Hrs./Yrs. Can A Well Maintained Diesel Last?" See especially posts by RichH and carlf

petersea · Apr 20, 2010

A couple of minutes of run time at the dock is all that is needed.(use this time to do a physical inspection of engine to make sure everything is OK) General speaking most people will run at a reduced speed leaving port and engine will get to operating temperature very quickly. Most engines will "cool off " just from reduced speed in a channel or harbor when returning and docking. If not a couple of more minutes is all you need.

Steve Dion · Apr 20, 2010

Actually it depends on your engine. If you have a fresh water cooled engine (heat exchanger) you can start it up, cast off the lines (and power cord; usually a good idea) and away you go. You can slowly increase the throttle until you are up to cruising RPM.

If you have a raw water cooled engine, it is best to let it warm up for several minutes. Many of these engine will stall if you apply power before it gets some heat in the cylinders.

Many of the early Yanmars were raw water cooled and a brief warm-up is a good idea.

alexco38 · Apr 20, 2010

Motor her a bit every year

Don't be such a purist on sail. It is OK to motor.

Once in a while when the wind isn't favorable I just motor sail her home. She need to work her "carbon" off anyway. And besides, I can burn off some old fuel thus save me the trouble of bring them to the recycling place.

On you way out, it is better to wait a few minute for the engine to warm up a bit so it won't stall when put in gear. One the way back, I usually let her idle until I tie the boat up properly before shut off the engine.

KD3PC · Apr 21, 2010

unless you have a turbo...then you need to wait a few minutes after a run for things to spin down, cool down and then shut her down.

I, contrary to the above, run long enough at the dock to make sure my pumps are working, that fuel is moving through the system without air in the lines. Water pump is pumping and the like..

Nothing like moving into a busy fairway, current or channel to have the engine quit...enough fuel in the pump to get you out...but then no more...did you forget a valve or is there sludge in the filters..

All the best

Honeyman · Apr 21, 2010

I do my best to run mine a min. of 30 minutes heading out and coming back in. More important, and this is straight from Mack Boring Diesel School, at least once a month act like you own a power boat and get out and run at close to WOT for an extended length of time, 2-3 hours, to help blow out carbon. Our diesels are designed to run at 75-80% of WOT for life, with a load on them.

Benny · Apr 21, 2010

Even though engine oils have substantially improved over the years I think it is still a good idea to warm up a 1980 engine especially if it is raw water cooled. Allow a couple of minutes at fast idle to let all those different engine metals to gradually expand and for the oil to reach operating temperature. A cold diesel will have a "clickety-clack" noise to it that will soon disappear as it warms up and you may get underway at this point gradually increasing the load. A cool down period is also recommended to allow the engine components to return to their idling speed temperature. Unless the engine was being driven hard or there were signs of overheating this cool down period need not be but a couple of minutes at idle.