On a recent trip back from the Channel Islands to
San Diego, the port
engine on a 65 foot powerboat with Detroit 8V71's began
overheating at anything over about 1350
RPM. Checked the
raw water strainer, all hose connections, etc.
Heat exchanger had been rebuilt less than 500 hours before.
I decided to run the starboard
engine around 1500
RPM but backed off on the port engine to about 1250 RPM that kept the temp gauge below 195 F. As we entered
San Diego, the port engine began to blow black smoke, a sure sign the blower was stuffed up with unburnt
fuel.
Now looking at a big
repair bill plus an awful mess to clean up on the transom and stern windows.
Have not yet checked out the
water pump">raw
water pump on the engine which may be the culprit, however, I doubt it.
I feel a bit of an idiot for not scoping the
overheating problem out sooner when we were anchored.
The
boat had not been used for several months but ran fine on a few turns around the harbor to check out the systems for a couple of hours. Also, she performed well on her trip to the Islands, about 85 NM's one way.
I guess the reason I'm
posting this is to let others learn from my mistake of not running the engines up to proper operating temp under load and watching for oveheating signs for a considerable period of time.

Capt Phil