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Old 15-04-2018, 21:07   #1
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Propellers

I have a 50hp Perkins with shaft drive & a 2 blade bonze prop which is badly pitted & needs replacing. I'm guessing its the original prop.
Would there be any advantage in changing for a 3 blade prop, or should I just leave things as they are?
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Old 15-04-2018, 23:27   #2
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Re: Propellers

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Originally Posted by Harro View Post
I have a 50hp Perkins with shaft drive & a 2 blade bonze prop which is badly pitted & needs replacing. I'm guessing its the original prop.
Would there be any advantage in changing for a 3 blade prop, or should I just leave things as they are?
No doubt moving to a 3 blades prop gives you the following advantages:
Less prop slip
Less noise
Better speed forward, especially against wind and sea
Better reverse power

Than moving to stainless steel would also give you the advantage of higher corrosion resistance and no pitting issue
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Old 16-04-2018, 01:56   #3
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Re: Propellers

Thanks for the advice.
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Old 16-04-2018, 03:16   #4
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Re: Propellers

The charts on propeller tests suggest an increase in drag with 3 blades over 2. If this is acceptable then fine, if not perhaps stay with 2 blades. How old is the prop and is it well protected with an anode? There will be a reason for the pitting, whilst stainless will help resist this, how about solving the underlying problem.

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Old 16-04-2018, 03:30   #5
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Re: Propellers

Iíve always believed that stainless is more likely to have issues with corrosion than bronze...
Curious...
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Old 16-04-2018, 05:32   #6
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Re: Propellers

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The charts on propeller tests suggest an increase in drag with 3 blades over 2. If this is acceptable then fine, if not perhaps stay with 2 blades. How old is the prop and is it well protected with an anode? There will be a reason for the pitting, whilst stainless will help resist this, how about solving the underlying problem.

Pete
Thanks Pete. The prop was badly pitted when I bought the boat 2 years ago. It is protected with an anode. Being bronze I'm thinking it would be easy enough to have reconditioned?
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Old 16-04-2018, 07:51   #7
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Re: Propellers

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Being bronze I'm thinking it would be easy enough to have reconditioned?
Completely dependent upon how badly corroded the metal is.
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Old 16-04-2018, 08:00   #8
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Re: Propellers

A 3 blade will be an improvement, especially in stopping thrust. There is an MIT test on props which indicated the Michigan Sailor, with the narrower blades and less drag is more efficient that the big mickey mouse ear models, or at least equal IIRC. Google the test.
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Old 16-04-2018, 08:35   #9
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Re: Propellers

For almost the same price as a regular Michigan 3 blade you could get a Campbell sailor prop with the added benefits of less drag, reduced prop walk while giving more thrust in both forward and reverse. http://www.westbynorth.com/campbell-sailer/
https://forums.sailboatowners.com/in...sailor.112587/
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