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post #4 of Old 07-13-2011
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Originally Posted by Hartley18 View Post
Here's a question: I know that all marine diesels need to be run at least every two weeks to (a) minimise the risk of seawater corrosion in the cooling passages and (b) top off the staring batteries. I've also heard that running a marine diesel off-load for long periods of time can coke up the cylinders reducing it's life, so:
Where did you hear that? Are you referring to a raw water cooled diesel or a fresh water cooled diesel? Either way, whether the engine is running or not, there will be seawater sitting in the cooling passages. So running the engine won't change that.

You do need to keep the batteries charged, but you don't need to run the engine every other week to do that. You can use solar, shore power, or just let them run down, and bring a jump pack on board in case they get so weak they won't start the engine.

Batteries are a lot cheaper than a new engine!

Originally Posted by Hartley18 View Post
Assuming a boat is sitting on it's mooring over a long period of time and never used, ideally, to get the longest life out of engine and batteries, assuming the engine is run at least every 2 weeks, for how long should you run the engine each time, at what load and at what speed??

Idle? Above Idle? In gear? Out of gear??

No-one I've spoken to seems to really, definitively, know the answer to this, and yet hopefully there are some diesel experts around here who know the answer. Let's hear it.
If this were my boat (and if I wasn't going to use my boat often enough I would probably just haul it or sell it), I would start the engine once a month, drop the mooring, and motor at 80% power for 15 minutes or so.


Barry Lenoble
Deep Blue C, 2002 C&C 110
Mt. Sinai, NY

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