Is it true that it is better to run a marine diesel engine in gear while idling? If so, why?

Answer 1

+ It depends on the size and weight of the shaft. If it is a large heavy shaft, you should keep it turning. There is usually an auxiliary gear to do this when in-port, or a small electrical motor. A 400 foot destroyer typically runs the shaft at a couple of revolutions per hour in port. It does two things. It keeps the shaft from sagging between bearings and it keeps the bearings rolling so they remain round. It should not even be a consideration in a small boat less with than 40 foot of shaft length and less than 100 lbs per foot shaft of length/weight(the bearings are made to withstand the stress).
Your answer would be no, as the requirement is done by other means than the marine diesel engine being engaged to the shaft.

Answer 2

The above 3 answers are wrong. It is all very well to "turn up at the boat once a week and run the engine" . Yes this is a good idea but.. you are only running the engine. Firstly It despite what the temperature gauge says will not fully warm up to operating temperature, thus causing cold spots on the cylinder bores and then excessive oil comsumption, Also it causes the oil to "sludge up". Place "spring lines" fore and aft and if there is not a lot of use of the vessel run her in gear for at least an hour on each shaft. While you are doing that be sure to run all of the ships systems (refrigeration, electrics etc). what this does is to alow the machinery to warm up properly, prevents the lubrication in stern glands or legs from drying out, And cycles the batteries properly

Answer 3

If in gear, the boat will be moving. Not a good idea.

Answer 4

No not true why would you want to,maybe for safety but not good on anything.

Answer 5

NO it is not true_________