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Old 01-05-2014, 18:11   #1
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Shaft length

Bought a 1971 32' Irwin as a fixer upper. Motored about fifty miles to have it hauled. No problems. The shaft is a little over a foot long and there is no strut. The original engine was an atomic four but was replaced with a universal diesel. Would the transmission be longer and cause the prop to be so far out. If you have a 32' on the hard, what is the length of the exposed shaft? Maybe I just need this one cut. Pacerow

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Old 01-05-2014, 18:55   #2
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Re: Shaft length

You need to get the hacksaw out. Leave enough room for a zink and maybe a rope cutter.. Oh, plus 1/3 the cord of the prop...

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Old 01-05-2014, 19:34   #3
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Re: Shaft length

pacerow, it probably should look like this.

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Old 01-05-2014, 19:34   #4
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Re: Shaft length

I have read that the maximum recommended length from the strut or deadwood should be no more than 1.5 times the shaft diameter. However, there should be at least 10% of the prop diameter clearance between the prop blade tip and the hull of the boat.

That being said, I have seen props sticking out a foot or more from a strut with no apparent consequences.

Fair winds and calm seas.
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Old 13-06-2014, 00:35   #5
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Re: Shaft length

The longer the unsupported length past the cutless bearing, the higher the risk of vibrations or bending the shaft if the prop catches something.

If it is running smooth, you don't have a problem with it, so you can make a call.

I have designed high-efficiency motor yachts where I extended the stern tube out from the back of the keel and pushed the shaft out a little as well to get better, cleaner water to the propeller. If the shaft diameter is big enough and the whole system well aligned, balanced and engineered, no problem.
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