I have a 245 with a two blade propeller. Over the last couple of years it has become apparent that the boat (with a Yanmar 1GM10) does not have enough puff for the conditions on the Thames. I am advised to upgrade to a 3 blade prop to increase thrust. Can anyone suggest a good supplier for a new prop? My shaft is 25mm dia. I cannot find a gearing ratio on the gear box. Thanks Steve
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No increase in thrust
If your 2 bladed prop is reasonably matched to your engine, there will be no increase in thrust against wind or tide. 3 blades can improve acceleration coming out of waves, but not average power delivered. David Lady Lillie
If your 2 bladed prop is reasonably matched to your engine, there will be no increase in thrust against wind or tide. 3 blades can improve acceleration coming out of waves, but not average power delivered. David Lady Lillie
I'm with David
Especially given a 1 hp engine, three-blade seems overkill. Perhaps it would help to eye the tides and take advantage of them in making you day plans.
Especially given a 1 hp engine, three-blade seems overkill. Perhaps it would help to eye the tides and take advantage of them in making you day plans.
three blade prop is the way to go
Changed this year to a three blade prop and wished I had done it years ago. The small 2QM15 engine rated at 14 hp now pushes the boat with ease. Here is a link on why the three blades are better than two. A good place to buy props is Admiral/C&B Propeller 888-398-8558 - this is their web site http://www.acbprop.com/ I purchased a used prop from them. It looks like they have free shipping.
Changed this year to a three blade prop and wished I had done it years ago. The small 2QM15 engine rated at 14 hp now pushes the boat with ease. Here is a link on why the three blades are better than two. A good place to buy props is Admiral/C&B Propeller 888-398-8558 - this is their web site http://www.acbprop.com/ I purchased a used prop from them. It looks like they have free shipping.
Paul - your links
seem to say that a well designed three blade prop will perform better than the "standard" design. My assumption is that prop design is so well known that both propellors have good designs. And I studied prop design long enough to stick with my statement for low speed (2 to 7 knots) props working in water. I have neither experienced nor heard of the vibrations mentioned as both blades are "hiding" at the same time. Threads on this site about propulsion vibrations have all come up with some other cause. In fact, on Lady Lillie, and on any design with a shaft strut, the bottom blade is not obstructed as it rotates through the centerline. Finally, regardless of Admiral's thoughts about dragging a hand in the water, most discussions on this site have conceded a lost half knot or more under sail. That's a big penalty (10% of cruising speed) to pay for minimal advantages. If "conditions on the Thames" means tide and wind, I doubt three blades will help much. If it also includes bucking substantial waves (as we often have on Lake Erie) then the third blade will help in accelerating out of the waves. I'd pay more attention to the Admiral sales pitch for three bladed props if they cited any research to back up their claim. David Lady Lillie
seem to say that a well designed three blade prop will perform better than the "standard" design. My assumption is that prop design is so well known that both propellors have good designs. And I studied prop design long enough to stick with my statement for low speed (2 to 7 knots) props working in water. I have neither experienced nor heard of the vibrations mentioned as both blades are "hiding" at the same time. Threads on this site about propulsion vibrations have all come up with some other cause. In fact, on Lady Lillie, and on any design with a shaft strut, the bottom blade is not obstructed as it rotates through the centerline. Finally, regardless of Admiral's thoughts about dragging a hand in the water, most discussions on this site have conceded a lost half knot or more under sail. That's a big penalty (10% of cruising speed) to pay for minimal advantages. If "conditions on the Thames" means tide and wind, I doubt three blades will help much. If it also includes bucking substantial waves (as we often have on Lake Erie) then the third blade will help in accelerating out of the waves. I'd pay more attention to the Admiral sales pitch for three bladed props if they cited any research to back up their claim. David Lady Lillie
Reduced three blade size
My experience was in going from a two blade 14X12 to a three blade 13X11, with that the rpm gain was from 1.900 to 2,400. In neutral the rpm is 2,800. The engine/shaft is much smoother and the speed under power with no wave is 6.3-6.4 knots. Against wave and wind she hold well above 5 knots. The two blade was a big square shaped prop which likely was a drag on sailing speed. The Hunter 33 it is on, is a fairly light boat and seems to sail as well today as it did before the change in props. The boat is not raced. If it were some kind of folding feathering prop would be required.
My experience was in going from a two blade 14X12 to a three blade 13X11, with that the rpm gain was from 1.900 to 2,400. In neutral the rpm is 2,800. The engine/shaft is much smoother and the speed under power with no wave is 6.3-6.4 knots. Against wave and wind she hold well above 5 knots. The two blade was a big square shaped prop which likely was a drag on sailing speed. The Hunter 33 it is on, is a fairly light boat and seems to sail as well today as it did before the change in props. The boat is not raced. If it were some kind of folding feathering prop would be required.
3 blade
Thanks Paul. What company did you get your new 3 blade prop from? I also have the problem that the engine is not developing enough revs. Thanks Steve
Thanks Paul. What company did you get your new 3 blade prop from? I also have the problem that the engine is not developing enough revs. Thanks Steve
Prop source
Steve, it was a used prop from Admiral/C&B Propeller 888-398-8558 in Tampa, FL. In that the boat is 28 years old I decided to go with used rather than new. It was the only one that they had in a size that fit. It works well. Link below
Steve, it was a used prop from Admiral/C&B Propeller 888-398-8558 in Tampa, FL. In that the boat is 28 years old I decided to go with used rather than new. It was the only one that they had in a size that fit. It works well. Link below
local prop dealer
I am guessing you are talking about the Thames River in Connecticut. If so try Hale Propeller in Old Saybrook Ct. I did some business with them about three years ago and was very happy with everything. Check out the attached link.....
I am guessing you are talking about the Thames River in Connecticut. If so try Hale Propeller in Old Saybrook Ct. I did some business with them about three years ago and was very happy with everything. Check out the attached link.....
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