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Old 16-01-2014, 21:42   #1
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Propeller life

How long does a propeller last on a sailboat? 14 inch two (fixed) blade Martec, if it matters.

I'm sure there are many variables - damage, zinc replacement frequency...

But is a 14 year old prop apt to be mostly used up? I found a receipt dated 1997 in the ships papers.

When my boat was surveyed the surveyor rapped on my prop with a piece of metal and said it "didn't make a ringing sound like it should." I talked to a prop shop since and they said when I haul out (very soon) to bring it to them and they will sandblast and check it out, that no prop makes a ringing sound when on the shaft.

I'd like to change from a two bladed prop to a three bladed Campbell Sailer if it is time (or nearly time). I'd not like to be racking up boatyard fees while I have one made and shipped, or racking up charges at a prop shop tinkering with a prop that is nearing end of life.

Even after aligning the engine the boat has vibration I'm hoping the prop change would help with, but it's "on my list" mostly for the surveyor's concerns.

Greg
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Old 16-01-2014, 22:02   #2
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Re: Propeller life

Other than physical damage from being hit or catching line, or catastrophic galvanic corrosion I have never heard of a prop wearing out. They are big, bronze, and have no moving parts.

I guess over long enough the keyway could wear out, but I have never seen or heard of it happening. But saying that I am sure someone will jump in here with it having happened to them.
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Old 16-01-2014, 22:39   #3
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Re: Propeller life

The prop may need to be rebalanced. That could be causing your vibration.

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Old 16-01-2014, 23:09   #4
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Re: Propeller life

Quote:
Originally Posted by Stumble View Post
Other than physical damage from being hit or catching line, or catastrophic galvanic corrosion I have never heard of a prop wearing out. They are big, bronze, and have no moving parts.

I guess over long enough the keyway could wear out, but I have never seen or heard of it happening. But saying that I am sure someone will jump in here with it having happened to them.
A prop that has been allowed to cavitate can wear badly but it's very obvious.
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Old 17-01-2014, 06:17   #5
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Re: Propeller life

I can guarantee that tapping a prop blade even while on the shaft will produce a ringing sound. It will not reverberate and sustain like it would if the prop were free and suspended from a string but the sound will be there.

What to listen for is akin to listening for dry rot when tapping wood. Good wood or metal will ring, soft will have more of a thunk or thud. The sound can be subtle and if the damage is slight may be very subtle.

On a bronze prop what you are looking for is loss of zinc in the alloy. Another and perhaps better way to check this is visually. Shine up the prop and look for areas that the color is going pink instead of the yellower shade of good bronze. The pink is an area where the zinc is lost and you are seeing more copper.
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Old 17-01-2014, 13:38   #6
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Re: Propeller life

I dug out the survey. The condition of the prop wasn't called out under his major findings, but where he inventories propulsion he says "Galvanic corrosion has softened metal." It's been in the water a year since then. I guess if I'm looking for an excuse to upgrade I have that and, "But honey, it's for the safety of our family."
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Old 17-01-2014, 16:49   #7
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Re: Propeller life

Used props are worth their weight as scrap, assuming you can find a boat scrapper that hasn't recycled them yet. There are a couple of places in Florida that scrap hurricane boats that always have a pile of them in the back somewhere, the trick of course is finding the right size.
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