Thread: One Engine
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Old 08-16-2013, 09:29 PM   #16
twistedtree's Avatar
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 4,230
Lots of good advice here, but let me add a couple of other considerations:

- Don't confuse the economy gained by going slower with economy gained by shutting down one engine. I've seen lots of claims of greater fuel economy by shutting down one engine, when 90% of the gain simply comes from operating at a lower speed. Run at that same slower speed with two engines and you will realize 90% of the gained economy.

- If your gear box and shaft seal cannot freewheel then you are likely to lose all gained efficiency by dragging around a locked prop. In fact, your efficiency may actually be worse than running with two engines.

- Check to be sure your gear box can be freewheeled, but also be sure to check your shaft seal. Many dripless seals require raw water flow which comes from a RUNNING engine. No running engine, no water flow, overheated shaft seal and possibly cuttlass bearings too. This is one of the biggest areas the check when people say "it depends".

My personal assessment is that any gains from running one engine is splitting hairs at best, and a false economy at worst. Throw in the risks and complications of damage cased by excessive freewheeling, and it's just not worth it.
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