i have just purchased a 1987 hunter 31, im thinking about changing the prop to a 3 blade. does anyone know what size and pitch to use. the prop on the boat is a 17/10 2 blade. thanks
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J
John Edmundson
my '87 31' has a 12x15 2-blade prop
Curious that our props would be so different. Mine came with the boat 4 years ago. I have no idea if it is the original. Why are you going to a 3-blade? My prop propels us at hull speed at 3200 RPM.
Curious that our props would be so different. Mine came with the boat 4 years ago. I have no idea if it is the original. Why are you going to a 3-blade? My prop propels us at hull speed at 3200 RPM.
Jeff, are you sure?
Jeff: The stock prop was about a 15 x 12. My exterience was that it was slightly over-propped with this prop. I got a CDI prop several years ago and it was more like 15 x 11. I would think that a 15 x 10 would be just about perfect (on our boat). It would allow the engine to rev all the way to the max rating and would not smoke. I have to agree with John, why do you think you want a 3 bladed prop? I suppose you may want to sail a little slower?
Jeff: The stock prop was about a 15 x 12. My exterience was that it was slightly over-propped with this prop. I got a CDI prop several years ago and it was more like 15 x 11. I would think that a 15 x 10 would be just about perfect (on our boat). It would allow the engine to rev all the way to the max rating and would not smoke. I have to agree with John, why do you think you want a 3 bladed prop? I suppose you may want to sail a little slower?
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jeff
steve and john
i measured the prop yesterday it measured 17" and when i cleaned off the #s it said RT 17 10 the reason for a big prop is to get this boat from lake michigan to the saginaw bay. last year i made this trip and got my butt kicked by mother nature. since i wrote this i started thinking about what the previous owner said that he motors at 6.4 to 6.8 knots and maybe he isent stretching the facts? the spects sheet says that mischief should have a 15/12 but it dosent make any provisions for the change in horse power from 84 to 87. so now im on the fence do i stick with the 17/12 and hope that it will push well in to weather or chang it?
i measured the prop yesterday it measured 17" and when i cleaned off the #s it said RT 17 10 the reason for a big prop is to get this boat from lake michigan to the saginaw bay. last year i made this trip and got my butt kicked by mother nature. since i wrote this i started thinking about what the previous owner said that he motors at 6.4 to 6.8 knots and maybe he isent stretching the facts? the spects sheet says that mischief should have a 15/12 but it dosent make any provisions for the change in horse power from 84 to 87. so now im on the fence do i stick with the 17/12 and hope that it will push well in to weather or chang it?
M
Michael O'
Folding Prop $$
If you go 3-bladed, then why not spend the money and get a folding prop?? The drag when sailing will really frustrate you in light air. I stayed with a two blade Gori folding prop when I made the change. It's been great for 18 years!
If you go 3-bladed, then why not spend the money and get a folding prop?? The drag when sailing will really frustrate you in light air. I stayed with a two blade Gori folding prop when I made the change. It's been great for 18 years!
G
Guest
I'm running a 14/11 3 blade...
I've got exactly the same boat, and I switched from my 2-blade to a fixed 3-blade prop recently. I beilieve my 2 blade prop was 15/12, though. I called Hunter and they put me on to General Prop, who apparently supplies their propellers, and the guy there was really helpful and suggested the size and pitch of a 3 blade with reference to the existing prop. Anyway, I know there are a lot of folks who don't like the idea of a 3-bladed prop on a sailboat, but if you are contending with motoring into big winds and a lot of chop sometimes, as I am, the 3-bladed prop is a significant improvement. Moreover, the 3-blade prop seems to run a lot smoother, over a wide rpm range. If you have a lot of wind most of the time, as we do in SFO, the extra drag is not a factor; If folding props weren't so friggin' expensive, that would be the way to go I'm sure, but I think the fixed 3-blade prop pays off every once in a while when you really need it. The only thing that surprised me was that the 3-bladed prop has a tendency to 'windmill' under sail, and there's a forum discussion from a week or 2 ago that concluded, as far as I could tell, that windmilling props cause people to drink more, or something like that. P.S. - You'll love the boat, either way.
I've got exactly the same boat, and I switched from my 2-blade to a fixed 3-blade prop recently. I beilieve my 2 blade prop was 15/12, though. I called Hunter and they put me on to General Prop, who apparently supplies their propellers, and the guy there was really helpful and suggested the size and pitch of a 3 blade with reference to the existing prop. Anyway, I know there are a lot of folks who don't like the idea of a 3-bladed prop on a sailboat, but if you are contending with motoring into big winds and a lot of chop sometimes, as I am, the 3-bladed prop is a significant improvement. Moreover, the 3-blade prop seems to run a lot smoother, over a wide rpm range. If you have a lot of wind most of the time, as we do in SFO, the extra drag is not a factor; If folding props weren't so friggin' expensive, that would be the way to go I'm sure, but I think the fixed 3-blade prop pays off every once in a while when you really need it. The only thing that surprised me was that the 3-bladed prop has a tendency to 'windmill' under sail, and there's a forum discussion from a week or 2 ago that concluded, as far as I could tell, that windmilling props cause people to drink more, or something like that. P.S. - You'll love the boat, either way.
Not propper tip clearance.
Jeff: I think you will find that if you contact a prop shop that you will get some good advice on how to size a prop. Typically you need to have propper clearance between the tip of the prop and the hull. This is one of the biggest problems with prop walk. I suggest that you get some expert advice before you invest any money is upgrading or modifying what you have. My '85 has the same engine as your boat and we use a 15" prop. I believe that our tip clearance was about 1.75". PS: How many RPM's are you able to turn at Wide Open Throttle (WOT)? You should be able to turn 3400-3600.
Jeff: I think you will find that if you contact a prop shop that you will get some good advice on how to size a prop. Typically you need to have propper clearance between the tip of the prop and the hull. This is one of the biggest problems with prop walk. I suggest that you get some expert advice before you invest any money is upgrading or modifying what you have. My '85 has the same engine as your boat and we use a 15" prop. I believe that our tip clearance was about 1.75". PS: How many RPM's are you able to turn at Wide Open Throttle (WOT)? You should be able to turn 3400-3600.
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jeff
steve
the last time i was at the boat it seemed to have around 1" of clearance between the hull and the prop. hopefully the boat will be in the water this weekend, and i will be able to water test it. as long as i dont have a problem with prop wash or excessive prop walk i will leave it alone. i will post the results on this site. jeff
the last time i was at the boat it seemed to have around 1" of clearance between the hull and the prop. hopefully the boat will be in the water this weekend, and i will be able to water test it. as long as i dont have a problem with prop wash or excessive prop walk i will leave it alone. i will post the results on this site. jeff
RPM's are the other consideration
Jeff: You want to make sure that you are getting the max RPM's out of your engine. You should be running your engine at 2500-3000 rpm's when cruising. These are critical numbers for engine longevity.
Jeff: You want to make sure that you are getting the max RPM's out of your engine. You should be running your engine at 2500-3000 rpm's when cruising. These are critical numbers for engine longevity.
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