3-bladed prop on Pearson 303 - SailNet Community

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  #1  
Old 11-27-2011
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3-bladed prop on Pearson 303

Any advice on switching from a 2-bladed to a 3-bladed prop on my 1983 Pearson 303? Valued advice would be dia., pitch, same reduction gear ratio?; all this powered by a 2GMF Yanmar. Is this asking too much of the 2-banger, and any other considerations would be helpful in a decision.
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Old 11-27-2011
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Why do you want to put a three blade on? A two blade should do the job just fine.
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Old 11-27-2011
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A 3 blade should be smoother and if the right diameter and pitch is chosen your engine will not have a problem. One 3 blade that would be a good choice is the Campbell Sailor which has the least drag of any fixed 3 blade prop.
West by North Enterprises - Campbell Sailer

This is interesting reading as well: West by North Enterprises - Choosing a Propeller
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Old 11-28-2011
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Why are you considering a switch? If its poor performance, make sure your current prop is sized correctly. This link lists some suggested props for different engine/transmission combinations.

props by motor and gear ratio

I would first compare your prop to the ones listed there for your engine to see where you are. Note you need your transmission ratio.
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Old 11-28-2011
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If diameter and pitch are correct a two blade is much better performancewise. Three blade is smoother than a two blader. If you are happy with the smoothness of your prop do not replace it, you will loose performance.
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Old 11-28-2011
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Absolutely

Quote:
Originally Posted by celenoglu View Post
If diameter and pitch are correct a two blade is much better performancewise. Three blade is smoother than a two blader. If you are happy with the smoothness of your prop do not replace it, you will loose performance.
A Pearson 303 is already "slow", putting a 3-balded prop will only make it slower. If you're really thinking about putting a 3-bladed prop, think about a feathering one.

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Old 11-28-2011
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All the above comments are valid. I would add that a two blade can be positioned behind the deadwood and drag is much reduced when sailing. How much a 'grip' the propeller has on the water depends on diameter and pitch, not the number of blades. Diameter is by far the most important. The reason for a three blade is usually cavitation where the forces are so strong that vapor forms at the face of the propeller and then collapses causing severe erosion of the metal. If the propeller is sized large enough, the forces are small enough to not cause this to happen. The marine architect that designed the boat would have worked this out with the choice of a propeller that would not cavitate and would be properly sized so that the engine would transfer its peak horsepower when at maximum rated RPM. If you do not have the original engine, then we need to take a careful look at the propeller that’s there and see if it is properly matched to the engine. This takes a lot of time to work out. The original prop is a 16X10 two blade with a 13 HP engine. I would prefer a 20 HP for bucking the wind with a 10,000 pound boat. If you want the best performance and fuel economy, buy a Max-Prop where the engine torque is near maximum for a given RPM. Saves about 20% in fuel because less unused air is pumped through the diesel engine (pumping losses). A 16” two blade is about $2000 and will fully feather when engine is off.
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Old 11-28-2011
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FWIW, my P323 has a 3-blade prop. I am happy with the power/smooth running; but I also agree that the drag makes my baby - never fast - even slower. I intend to move to a folding prop when finances allow.
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Old 11-29-2011
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A fixed prop is never as efficient as a folding prop under sail, but a fixed three blade is a great cost effective solution if you need performance under power, if it is the proper pitch and dia for your engine. And an even better idea, if you can afford the price of admission, is a KIWI 3 blade folder. Best of both worlds and not a deal killer price. Pat

Last edited by Cherie320; 11-29-2011 at 01:09 AM.
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Old 11-29-2011
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Kiwi are feathering props - they do not fold. The Kiwi Feather Propeller Home Page
Attached Thumbnails
3-bladed prop on Pearson 303-1.jpg   3-bladed prop on Pearson 303-2.jpg  
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