Dan, did you check the little tube and hose on the installed rear end of the
engine, about 5 inches long? Hard to see and missed by many surveyors.

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Dan
Diesel engines should be run hot. Running them cold for a short period shouldn’t cause any harm however. I see no reason that you couldn’t pull the thermostat and run the engine for a few hours.

From your description, it sounds like it overheats even if you back down the throttle to run the engine with less load. If the engine is pumping adequate seawater through the exhaust, I would guess the problem is on the engine coolant side of the system. Either a stuck thermostat or air getting into the water pump and causing it to lose its prime. If air is getting into the coolant system, anti-freeze would be displaced. Is your overflow bottle overflowing? You may have to prime the water pump. This can usually be done by loosening a coolant hose and allowing the trapped air to escape. Someone more familiar with the W-58 could probably give you specific instructions.

Rich

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If you have a leak in the system, the airlock problem will repeat itself. If
you do not have all the pressure gauges and tools to pump up the coolant
side and see if it holds pressure, then run the engine with the cover on
the expansion tank off the tank. Usually air will rise to the highest point
in the system. Once water starts to expand (and it’ll be hot) and fills the
expansion tank, top off with mixture of anti freeze and water in to the
tank, and reseal. This will temporarily remove air from the system and fill
it up. Once it begins to exceed 100 C it may evaporate if there’s a leak in
the system , introducing more air. If it happens again then you know there’s
a leak in the system. Then you buy the pressure gauge item, and mix some
soapy water, and find the culprit that bubbles, by covering every junction
with soapy water. If there’s no sign of a bubble but it loses pressure, it’s
your heat exchanger.

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You know, if you suspect the thermostat you  can test it by putting it in a pan of water water and heating it on the stove and observe at what temp it opens. Then cooling it and see if it closes again.
alan

— On Mon, 5/17/10, kalinowski <> wrote:

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Dan-
There is a problem in running a W-58 without a thermostat. The disk on the bottom of the thermostat closes off a loop circuit from the engine to the fresh water pump. Unless this closes, coolant will not circulate to the heat exchanger. See the Westerbeke Parts List. If you don’t have a copy, look on line at most Westerbeke dealer web sites.
Suggest you get an IR thermometer (one of those gun shaped things) and use it to figure out exactly where on the engine theoverheating is occuring.
Quent

A coolant leak may show up as a white powdery “mustache” around the joint where the leak is. The gasket between the uppper and ower thermostat housings deteriorated and was passing small amounts of coolant. I use the “five year” heavy duty stuff, sort of gold-tan in color,omes in a gold container.
 
Norris Larson on Easy Reach, #206.
 

— On Mon, 5/17/10, Thatcher A. Stone <> wrote:

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I cannot cite part no. and detail, but in our boats, with the engine
reversed, at the top of the stern end of the engine is a metal tube and a
rubber hose. It is known to elude many a surveyor, as it is small, hard to
find, and can fail with leaks only at high, hot temps. As was the case with
my boat when I bought it.

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