I believe that my 1981 H-33 with the 2GM (13hp) is undersized. I am considering changing the prop from the current 14x12 2-blade to a three blade. I am hoping that this would give me better drive into the wind. Drag is not a concern as I do not race. One prop calculator gave me a size of approx. 13x11 but I was using design specs for the RPM (3600rpm). Unfortunately, my tach is broken so I cannot get an actual rpm at speed. Can anyone help me out with what rpm they use to achieve a desired cruising speed. I don't know if this will help me, but it sure won't hurt. Thanks, Scott
H-33 Prop Size Question
- Thread starter Scott A.
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I believe that my 1981 H-33 with the 2GM (13hp) is undersized. I am considering changing the prop from the current 14x12 2-blade to a three blade. I am hoping that this would give me better drive into the wind. Drag is not a concern as I do not race. One prop calculator gave me a size of approx. 13x11 but I was using design specs for the RPM (3600rpm). Unfortunately, my tach is broken so I cannot get an actual rpm at speed. Can anyone help me out with what rpm they use to achieve a desired cruising speed. I don't know if this will help me, but it sure won't hurt. Thanks, Scott
got 13x11 by default
Scott, funny you should get that number 13x11, as that is the three blade prop I put on my 33' this fall. I purchased it used (only used prop they had) from the best prop shop in the area. Wish I had made the change years ago. With the prop the RPMs are up from 1,900 to 2,300. For reference, in neutral the RPMs are 2,800. The power is up, the boat can now cruise 6.4-6.5 knots. The little 2QM15 Yanmar is as happy as its owner
Here is a good link describing why a three blade is far better than a two blade prop.
Scott, funny you should get that number 13x11, as that is the three blade prop I put on my 33' this fall. I purchased it used (only used prop they had) from the best prop shop in the area. Wish I had made the change years ago. With the prop the RPMs are up from 1,900 to 2,300. For reference, in neutral the RPMs are 2,800. The power is up, the boat can now cruise 6.4-6.5 knots. The little 2QM15 Yanmar is as happy as its owner
Here is a good link describing why a three blade is far better than a two blade prop.
got 13x11 by default
Scott, funny you should get that number 13x11, as that is the three blade prop I put on my 33' this fall. I purchased it used (only used prop they had) from the best prop shop in the area. Wish I had made the change years ago. With the prop the RPMs are up from 1,900 to 2,300. For reference, in neutral the RPMs are 2,800. The power is up, the boat can now cruise 6.4-6.5 knots. The little 2QM15 Yanmar is as happy as its owner Here is a good link describing why a three blade is far better than a two blade prop.
Scott, funny you should get that number 13x11, as that is the three blade prop I put on my 33' this fall. I purchased it used (only used prop they had) from the best prop shop in the area. Wish I had made the change years ago. With the prop the RPMs are up from 1,900 to 2,300. For reference, in neutral the RPMs are 2,800. The power is up, the boat can now cruise 6.4-6.5 knots. The little 2QM15 Yanmar is as happy as its owner
Here is a good link describing why a three blade is far better than a two blade prop.
Prop walk
Prop walk in reverse seems to be about the same as with a two blade prop. I have taken to backing into the slip and find that a fair amount of room is needed to get up to speed in reverse to be able to steer. The drill is to rev. up and gain way astern and then shift to neutral and steer into the slip.
Prop walk in reverse seems to be about the same as with a two blade prop. I have taken to backing into the slip and find that a fair amount of room is needed to get up to speed in reverse to be able to steer. The drill is to rev. up and gain way astern and then shift to neutral and steer into the slip.
just wondering how
While trying to back in too my slip in reverse,I just wonder when if the vessel is ever going to move.Then all of a sudden I start to go but awalys to port.I have a 13-11 three blade prop,my question is it prop walk or a trait.the time before it really starts to move makes one wonder.Wrong rpm ortide or just plain in experience,or all three.This is really a problem,just wondering if I am the only one,think of a cleat midships to jacknife the stern in atleast to get a start in slip.Really need some good advice.
While trying to back in too my slip in reverse,I just wonder when if the vessel is ever going to move.Then all of a sudden I start to go but awalys to port.I have a 13-11 three blade prop,my question is it prop walk or a trait.the time before it really starts to move makes one wonder.Wrong rpm ortide or just plain in experience,or all three.This is really a problem,just wondering if I am the only one,think of a cleat midships to jacknife the stern in atleast to get a start in slip.Really need some good advice.
Does it work?
Well that really is some prop.I sail out of a small gut off of Kent island,running aground seems like the norm around there.Did that prop give you enough power off a soft ground?The prop size I gave must have been wrong,it was from memory,and we all know how that works.The archives tell what size sheets are stock,but what have people found that works best?This is one subject that seems to have alot of confusion evoled with it,What are you using,and why?There is a old saying ,if you dont know ask someone that you think knows. I know everyone has there favorite but for a cruising and a all around sail for the money ,what is your bet?
Well that really is some prop.I sail out of a small gut off of Kent island,running aground seems like the norm around there.Did that prop give you enough power off a soft ground?The prop size I gave must have been wrong,it was from memory,and we all know how that works.The archives tell what size sheets are stock,but what have people found that works best?This is one subject that seems to have alot of confusion evoled with it,What are you using,and why?There is a old saying ,if you dont know ask someone that you think knows. I know everyone has there favorite but for a cruising and a all around sail for the money ,what is your bet?
Leslie and Chet
Funny you should ask Chet. The 2-blade Flex-O-Fold is here with me in New Port Richey, yep Florida. I brought it because Ed Allen wanted to check it out. I really think it is wrong for his H37C with that big 4-cylinder. But he has first dibs. Leslie I think the proper size prop assuming you have the 3-cyl is 15x13. For the 2-cyl it was 15x12. When I had to buy one along the Erie Canal that company also recommended a 15x13. But all that he had used was a 14x14 so that is what is on there. You probably read that the canal workers retrieved my Flex-O-Fold when they drained the canals for winter maintenance(a previous post here). Well that prop is on the boat and will be reinstalled at the next haulout in Oriental, NC. (Anyone up that way that can recommend a yard?)
Funny you should ask Chet. The 2-blade Flex-O-Fold is here with me in New Port Richey, yep Florida. I brought it because Ed Allen wanted to check it out. I really think it is wrong for his H37C with that big 4-cylinder. But he has first dibs. Leslie I think the proper size prop assuming you have the 3-cyl is 15x13. For the 2-cyl it was 15x12. When I had to buy one along the Erie Canal that company also recommended a 15x13. But all that he had used was a 14x14 so that is what is on there. You probably read that the canal workers retrieved my Flex-O-Fold when they drained the canals for winter maintenance(a previous post here). Well that prop is on the boat and will be reinstalled at the next haulout in Oriental, NC. (Anyone up that way that can recommend a yard?)
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