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How to exercise an unused engine

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Question: In your column, the questioner asked in part how often, how long, and at what rpm should he operate his engines before leaving his boat for two or three months or more? When I read the question, I said to myself, “Great—just what I’ve been wanting to know for several years now.” But here’s the deal. While your answer was terrific, it mainly dealt with the things folks should do when their boats are laid up for very extended periods or entire boating seasons. What about shorter periods? Sometimes I don’t have the time to actually take my boat out for two or three weeks at a time, but I do have time to run her Cummins diesels now and again. How often, how long, and at what rpm should I do this?

— Dick Alix Coronado, California

Professor Diesel: If you’re not using your boat for a while, even for a couple of months, there’s no need to start her engines. In fact, starting them at the dock and letting them run without bringing them up to temperature under load is normally not advised.

When you finally get ready to go out, devote a little extra preliminary care to your powerplants. Remember, they’re somewhat like human beings. When they lay around too long, their joints get stiff, their bones get sore, and it takes some time for them to get moving properly again

First, check for fuel, coolant, or lubricant leaks and correct if necessary. Also, check the belts on the alternators and belt-driven accessories for tightness and adjust as needed. Then make sure lubricant levels for engines, transmissions, and power steering are topped off.

Next, do a thorough check of all electrical harness connections on your engines. Look for wear, loose wires, or corrosion and address any and all issues.

Make sure the transmissions shift fully into forward and reverse, and the throttles move freely and fully. Make sure the prop-shaft couplings and engine mounts are secure. Finally, after checking all hoses and clamps and tightening and/or replacing whatever you need to, crank ’er up. Check for leaks, allow a little warm-up time, and then enjoy your day at sea.

Professor Diesel is Larry Berlin, director of Mack Boring’s Training Services division.