Outboard prop is always spinning. It that bad? - SailNet Community
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post #1 of 14 Old 07-12-2007 Thread Starter
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Outboard prop is always spinning. It that bad?

I have 2002 9.9 4 stroke Merc that hangs off the back. When I'm loaded with crew, and the engine is off and in the up position, the skeg and prop still drag in the water, causing the prop to turn at a fairly high rate of speed. I'm looking into a new bracket system, but I'm worried for now that the turning prop might be damaging the impeller or other internal mechanisms. Should I worry?
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post #2 of 14 Old 07-12-2007
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As long as the engine is in neutral, your fine.
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post #3 of 14 Old 07-12-2007
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outboard lower units are filled with oil the gears & bearings are soaked in this oil bath (something you should change annually) . the impeller is attached to the drive shaft comming down from the power head and does not turn unless the engine is running, so no added wear to the impeller. Your only worry should be floating objects which could strike the prop but then again that could happen when running the engine also.
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post #4 of 14 Old 07-12-2007 Thread Starter
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oh good news, thanks. I was worried. I actually started to worry after watching the show Deadliest Catch, one of the crab boats lost an engine and they had to chain the propeller shaft so it wouldn't spin, saying that the spinning prop would do serious damage otherwise. Which I still don't really understand, unless they couldn't get it out of gear or something.
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post #5 of 14 Old 07-12-2007
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I saw that episode also and had same question. The only thought I had was no oil pressure to lube bearings. But just a guess.
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post #6 of 14 Old 07-12-2007
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That's exactly the risk, unless the transmission is similar to my BW Velvet Drive, which has an integrated lube pump, separate from the engine.

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post #7 of 14 Old 07-12-2007
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Now if I could just remember - -> engine needs oil
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"Well boss, a diesel needs its oil like a sailor needs his rum"

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post #9 of 14 Old 07-12-2007
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Feathering the prop

A propeller when spinning generates lift which would increase drag. I think in the purest since that one's propeller should not spin unless it is driving the boat.

This is just my humble opinion. It has been 40 years since my college physics.

Probably doesn't make a lot of difference one way or the other.
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post #10 of 14 Old 07-12-2007
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With the recommendations of tranny integrated lube pumps, checking diesel oil, feathering props and sailor's rum . . . I suppose we're all getting a bit off-topic from knotaloud's 9.9 Merc OB prop spinning issue. < g >

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