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Warning..please read


tccombs

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I would be confident that this would only occur if there was some contaminant (sand etc) or a tuft of metal sticking out caught between the prop and shaft taper surfaces when the prop is installed. Such items can subsequently crush, work loose etc leaving a loose fit.

A neat, clean fit between properly machined tapers that are pulled together firmly with the retaining nut should remain tight.

I guess the ACME people are the most experienced experts but I've never heard of it.

Many, if not most of us, have changed at least one prop. I've done a bunch of them on several boats. Each one was fitted and tightened once and when it was time to remove it later, it sure needed some 'encouragement' to break it free from the shaft.

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I think this is a similar action as called "transient torque" in rotating shaft or electric motors. Where a electric power is interrupted in mili seconds then full power is reapplied. Causing a torque of up to 6 x normal on shaft causing breakages is what I have been told. So with a slight loose fit of the prop and internal combustion engine , I could see that but I believe manual calls for 30-40 ft lbs of torque on the shaft nut..I think the shaft key would shear first..???My 2cents. As long as prop is on tight,I do not see an issue. With that I am going to check my nuts

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I for one, am checking my nuts right now. If my shaft broke and fell off I would be quite sad.

Yes, you could be left somewhat idle with no means of thrust.

And someone might be pining that don't impress me much...

Edited by GreenMan
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As the result of a recent discussion here about engine alignment and how freely the prop should spin by hand, I decided to check mine. Grabbed the prop, and it wobbled noticeably! I assumed something had happened to the shaft key, but when I put the wrench on the prop nut to remove it I was shocked to find that it was already loose by about afull turn. Same prop, nut, and cotter pin have been in place for many years.

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Well, thanks for the warning. Poked my head under the boat and what did I see - a gap. Odd since I've never under tightened anything in my life.

attachicon.gifWP_20150930_002.jpg

That gap is typical. It is a tapered shaft and the prop will only go so far onto it. If the prop was in contact with the cutlass you would have metal rubbing on metal and that is a really bad thing. Almost as bad as when your shaft is broken and falls off.
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So did it snug up?

I tightened it up as well as I could but didn't have a 2x4 chunk handy so I need to try again later. Prop didn't seem to move at all. The nut spun pretty easy - one of the reasons I hate nylocks.

That prop has about 75 hours on it since installed.

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That gap is typical. It is a tapered shaft and the prop will only go so far onto it. If the prop was in contact with the cutlass you would have metal rubbing on metal and that is a really bad thing. Almost as bad as when your shaft is broken and falls off.

Talking about the air between the nut and the prop - the one that you could just about stick a dime in.

post-22501-0-51727300-1443639100_thumb.j

Edited by oldjeep
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