What's the advantage in a three bladed prop over a two. Would I gain speed, power or anything at all?
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Michael McCann
3 or 2?
David; Its very complicated, but you should have a gain in power, speed, and it will be smoother. Generally the pitch will be less on the 3 blade, but this depends on your engine, and transmission configuration. So yes you will see differences, but if it isn't done right you can damage your engine. Mike
David; Its very complicated, but you should have a gain in power, speed, and it will be smoother. Generally the pitch will be less on the 3 blade, but this depends on your engine, and transmission configuration. So yes you will see differences, but if it isn't done right you can damage your engine. Mike
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Trevor
flat vs. rough water
My understanding is that the overall speed through flat water will be similar but the 3 blade will provide considerably more power into chop or waves.
My understanding is that the overall speed through flat water will be similar but the 3 blade will provide considerably more power into chop or waves.
Depends!
David: Depends on your current prop too. If your current (2 bladed) prop is correct for the boat you should not see much difference between the two in flat water. A 3 bladed prop will tend to have MORE prop walk (if you have it now) assuming it is the same diameter. It should give you more punch in a lumpy seaway. It should slow you down under sail. If you do not have the propper prop now and you go to a 3 bladed prop that is correct for your boat, it may make all the difference in the world. A three bladed prop is usually better balance than a two bladed prop so you may find that it also runs smoother. If you decide to try this go to a prop specialist. They should be able to calculate the exact prop for your vessel. They need the engine specs, transmission ratio, approx. weight of the boat etc to do their calcs.
David: Depends on your current prop too. If your current (2 bladed) prop is correct for the boat you should not see much difference between the two in flat water. A 3 bladed prop will tend to have MORE prop walk (if you have it now) assuming it is the same diameter. It should give you more punch in a lumpy seaway. It should slow you down under sail. If you do not have the propper prop now and you go to a 3 bladed prop that is correct for your boat, it may make all the difference in the world. A three bladed prop is usually better balance than a two bladed prop so you may find that it also runs smoother. If you decide to try this go to a prop specialist. They should be able to calculate the exact prop for your vessel. They need the engine specs, transmission ratio, approx. weight of the boat etc to do their calcs.
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Bryan Cleveland
Power vs. drag.
A 3 blade prop has much more surface area than a 2 blade. The prop will "bite" much better. Your acceleration (forward and reverse) would be more responsive. A 3 blade prop has much more surface area than a 2 blade. It will add considerable greater drag. If you are already achieving hull speed with a 2 blade, you won't go any faster with a 3 blade. Might push you better thru the chop. All things being equal, if having responsive power (e.g. you have to maneuver thru a tight marina) is more important to you than optimal sailing speed you'd be better with a 3 blade. Best of all worlds would be a folding or feathering 3 blade, but then you are talking some $$$.
A 3 blade prop has much more surface area than a 2 blade. The prop will "bite" much better. Your acceleration (forward and reverse) would be more responsive. A 3 blade prop has much more surface area than a 2 blade. It will add considerable greater drag. If you are already achieving hull speed with a 2 blade, you won't go any faster with a 3 blade. Might push you better thru the chop. All things being equal, if having responsive power (e.g. you have to maneuver thru a tight marina) is more important to you than optimal sailing speed you'd be better with a 3 blade. Best of all worlds would be a folding or feathering 3 blade, but then you are talking some $$$.
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Del Wiese
powering into wind/chop
I have an 89 Legend 37 and according to the factory, "the gear reduction ratio on the Legend 37 Yanmar engine was 2.62 and the propellor that would have been speced for that boat was a 17 x 10 Right Hand 2 blade". I assume the propellor has not been changed and recently I motored 20 miles into a 20-25 knot headwind, with 2-3 foot chop and short pitched waves (on the shallow intercoastel waterway). The boat consistently managed 4.5 to 5.5 knots, at 2700 rpm. With no headwind she will manage 6-6.2 knots at this rpm. On a few occasions, the speed dropped to 4 knots when we smashed into a few waves in a row. I was pleased with this powering performance, although the trip was not fun!
I have an 89 Legend 37 and according to the factory, "the gear reduction ratio on the Legend 37 Yanmar engine was 2.62 and the propellor that would have been speced for that boat was a 17 x 10 Right Hand 2 blade". I assume the propellor has not been changed and recently I motored 20 miles into a 20-25 knot headwind, with 2-3 foot chop and short pitched waves (on the shallow intercoastel waterway). The boat consistently managed 4.5 to 5.5 knots, at 2700 rpm. With no headwind she will manage 6-6.2 knots at this rpm. On a few occasions, the speed dropped to 4 knots when we smashed into a few waves in a row. I was pleased with this powering performance, although the trip was not fun!
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Jack Beale
3-Blade = More Power
You will notice more power for starting and stoping and the time it takes to start or stop will be drastically reduced. You will notice less prop walk, as you have to give it less throttle for a smaller period of time to make the boat change directions. On the downside, you'll loose a bit of speed under sail - I'm told about 0.5 Kts (max) at top speed. Under power, you'll not see any signifigant speed increase or decrease, unless you are motoring into a heavy wind or sea. Then the greater 'bite' will provide more speed than the two bladed prop.
You will notice more power for starting and stoping and the time it takes to start or stop will be drastically reduced. You will notice less prop walk, as you have to give it less throttle for a smaller period of time to make the boat change directions. On the downside, you'll loose a bit of speed under sail - I'm told about 0.5 Kts (max) at top speed. Under power, you'll not see any signifigant speed increase or decrease, unless you are motoring into a heavy wind or sea. Then the greater 'bite' will provide more speed than the two bladed prop.
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Jack
Substantial Power increase
I once owned a Columbia 39 that came with a two bladed prop, and a small diesel engine that just wouldn't get up and go under power. I found an old timer (geltleman) in the propeller business in the area, and we changed the prop to the three bladed one that he recommeded. The speed increase was VERY substantial. I had been thinking of selling the boat due to its slowness under power, but the added new prop so chnaged the boat that I kept it for several yeras, and loved it.
I once owned a Columbia 39 that came with a two bladed prop, and a small diesel engine that just wouldn't get up and go under power. I found an old timer (geltleman) in the propeller business in the area, and we changed the prop to the three bladed one that he recommeded. The speed increase was VERY substantial. I had been thinking of selling the boat due to its slowness under power, but the added new prop so chnaged the boat that I kept it for several yeras, and loved it.
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Kevin L. Woody
Three blade
Dear David, A three blade is apx. 30% more efficient then a two blade. This increase of efficiency will help to maintain the boat speed when powering into a heavy wind or sea. The three blade will also help to reduce vibrations if the are present with the current two blade. With this increase in efficiency you will also see an added increase to the vessels response time when you are docking or simply going between forward and reverse. Hope this helps. Kevin
Dear David, A three blade is apx. 30% more efficient then a two blade. This increase of efficiency will help to maintain the boat speed when powering into a heavy wind or sea. The three blade will also help to reduce vibrations if the are present with the current two blade. With this increase in efficiency you will also see an added increase to the vessels response time when you are docking or simply going between forward and reverse. Hope this helps. Kevin
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