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Old 03-02-2014, 20:06   #16
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Re: Increase Propeller size?

G'day,
16''x12'' will do the job for you. This will give the 4.108 cruising sweet spot of around 2,200 to 2,300 rpm.
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Old 03-02-2014, 21:30   #17
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Location: Boat in Whitsundays, heading south.
Boat: Custom Perry Passport 41, steel
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Re: Increase Propeller size?

Quote:
Originally Posted by Downhill [IMG]file:///C:\DOCUME~1\david\LOCALS~1\Temp\msohtml1\01\clip_i mage001.gif[/IMG]
I'm looking to replace my fixed 3-blade 16" prop with a VariProp Feathering Propeller on my Morgan 323. The 16" propeller gives me roughly a 2" clearance between the blade tip and the hull. Here's the question:

Is a 1.5" clearance too tight if I would go with a 17" prop and is it even worth it with regards to power/thrust?

Any insight is appreciated.

Cheer![IMG]file:///C:\DOCUME~1\david\LOCALS~1\Temp\msohtml1\01\clip_i mage002.gif[/IMG]

Looks like you are now leaning towards fixed blade propeller.
So whats wrong with a16” Variprop.

Are you looking for faster sailing speed or what is it you looking for.

Think it’s the tip vortex phenomena that cause unwanted banging on your hull that is the main objection to small tip clearance. Another reason is the wake speed further out from the hull differs greatly in the vicinity of where your top blade and the bottom blade will be, less so further out.

Of course, less blades, bigger diameter, slower speed improves efficiency. But you will gain more by going to a folding prop if you do lots more sailing.

Pitch determines wake speed and is related to slip ratio, thrust, power etc. You could I think go for a 15” if vibration has been a problem, and increase your pitch.

Has vibration been a issue?, what is the reason for the change.
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Old 05-02-2014, 01:21   #18
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Re: Increase Propeller size?

The truth is a Perkins 4.108 is producing about 10hp at 1000rpm and about 25hp at 2000rpm. It stands to reason that you are not getting best performance or fuel economy from your boat.
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