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Thread: General Prop Discussion

  1. #1
    Administrator Papee's Avatar
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    General Prop Discussion

    Let's discuss the prop subject for general information.
    Two blade vs multiple blades
    Wood vs Composite
    Shorter wide blade vs Longer at more pitch
    Reduction or not?
    Maybe we can get some of this information in one place. As questions get discussed I'll update this post.

    Props come in many different configurations from two blade wooden or composite to multiple blades either pitched by markings on the prop to fixed shims at certain degrees. There are also many different blade shape designs. Choosing the right prop for your project is one of the most important decisions you will make.
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  2. #2
    Senior Geezer buster's Avatar
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    Re: General Prop Discussion

    Glad you brought it up Papee. I don't have much personel experience yet, mostly stuff I have read on these forums. I have a 084 engine on a 11' x 6' boat, and am anxiously awaiting your results before I purchase the prop for it!
    I talked to Chuck the other day and he suggested a three blade 60" IVO. Unless someone can come up with a better, more economical suggestion, I may go that direction. Incidentally I do have a belt reduction on it.
    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  3. #3
    Administrator Papee's Avatar
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    Re: General Prop Discussion

    The best performing prop is almost always not the cheapest. As I said in the original post, the prop is probably one of the most important decisions you will make in building your project. I'm sure that if Chuck recommended that prop it is the best prop for your application. What I hope to do here is tell you why that is the right decision. Your final drive ratio has everything to do with your prop choice. Talking to an experienced builder such as Chuck is the best thing you can do when choosing a prop. If he doesn't know the best prop for your build he will point you in the right direction.
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    Re: General Prop Discussion

    You are so right Papee about the drive ratio. On Ron's 084, we ordered a 1.69 to 1 ratio and a 60 inch 3 blade IVO and installed it when it came in. The 084 had the stock carb. When we ran it at max pitch the motor would turn 4100. The IVO was not enough prop. I couldn't understand this motor being that strong. We measured the pulleys and found we had a 1.89 to 1 instead of a 1.69 to one. We weren't getting enough prop speed for the 3 blade IVO with the 1.89 ratio. We had some new wood props from fl airboat props on the shelf, a 6030 and a 6038. The 6030 was not enough prop and the 6038 would only let the motor turn 3200. We wanted the motor to turn about 3600. So the 6038 was too much prop. We installed a 3 blade 60" warp drive at 15 degrees and that held the engine rpm to 3700. That's about where we want to be with the engine RPM but we were at 1957 rpm on the prop speed. Not enough prop speed for the design of the blade. The boat performed OK but it would be better with a little more prop speed. We were going to get a new bottom pulley made to change the ratio and Ron wanted to install a solex carb cause we had some lean issues with the stock carb. He made the intake manifold for the solex and installed it. Now he gained 500 RPM on the engine, from 3700 to 4200. Now he has enough prop speed but the engine may not last long turning it that much. He set the pitch at 20 degrees and brought the rpm down to 3700 but now the setup want push as good. Too much pitch for the blade design and the efficiency will fall off. We have ask Circle S Manufacturing to make us a set of 4 blade bow-tie plates for the Warp Drive blades to see how good it will work. Next week, we will get the 6038 back and it should be good with the performance the solex carb gave us.
    Things to note:
    The 084 is a torque, low rpm motor and want work as good with too low of drive ratio unless you have a prop that works good at low prop speed.
    The wood props we used were from FL Airboat Props and had ss leading edges and tips. It weights 5 lbs more than the Arrowprop.
    Small changes can increase the performane of the 084 to a level that leaves you prop searching.
    Thanks, Chuck

  5. #5
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Re: General Prop Discussion

    Pappy, thanks for starting this thread. I want to learn all I can before buying a prop.

    Chuck, thanks for the info on what you guys are doing. You know I'm going to be picking your brain more on this.

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  6. #6
    Administrator Papee's Avatar
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    Re: General Prop Discussion

    By design props have a certain RPM range they work best in. Fixed pitch props for direct drive use are figured by using a formula using horsepower. An engine of a certain horsepower will turn it's perfect match in prop at the right rpm for that prop. If you try to go to big in diameter or pitch the prop will slow the engine and will not be effective. The same with a prop too small or not enough pitch will run too fast and have the same result.

    In a direct drive setup the perfect match would be one that holds your rpms down to a comfortable level using the prop as a governor. The more prop you can turn the better the thrust. Providing you have the room for a larger prop you could use a reduction drive as a torque enabler to run a bigger prop.

    On my boat, I can only run up to a 56 inch prop so I choose to use the 52 inch prop that my motor will turn using direct drive. I just don't feel the difference in performance would be that great adding another 4 inches of prop or worth the extra expense adding the redrive. In the conditions I run it is not safe to run more that 30 MPH so the 40+ MPH that my boat runs is plenty for my use.
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  7. #7
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Re: General Prop Discussion

    Papee,

    That's good information. I don't need or want FAST. This is going to be a Mini Airboat after all. 30-35 MPH would be plenty fast for me.

    I do want to be able to get up on plane quick, and be able to throttle back down to a reasonably quiet cruise.

    Sounds like you're saying that I don't need a reduction drive after all, which is something I've been wondering about. I'd just as soon go with a direct drive if it'll perform like I want. It'd be one less thing to maintain and worry about.

    I "think" that I'd rather spend the $ up front on a good direct drive adjustable pitch prop than on a reduction drive, if it'll meet my needs better. I do NOT want to spend a lot of time and money experimenting with props.

    Thanks,

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  8. #8
    Administrator Papee's Avatar
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    Re: General Prop Discussion

    I wasn't saying you don't need a reduction drive, I was just adding more info for the thread. Chuck has you on the right track. My hull is not as wide as most hulls so I am limited. If I had a wider hull would I be using a redrive? The answer is yes.
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  9. #9
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Re: General Prop Discussion

    Papee,

    Thanks for clearing that up for me.

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  10. #10
    Senior Geezer buster's Avatar
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    Re: General Prop Discussion

    Chuck recommended a 60" IVO prop with a 1:69 to 1 ratio redrive when I called him the other day. When I got the redrive, It measured 4" X 6 15/16" pulleys. If I figured correctly that is 1:73 to 1 reduction. I am wondering if Chuck would still recomend the same 60" IVO, or something else. I have been given advise from others that should know, But Chuch seems to have his sh*t together. I'm not to sure about the rest of them!
    My cage is now set up for a 60" prop, so I hope I won't have to change that.
    I know Chuck is busy trying to make a living, so I hate to bother him again. If anyone has experience with props for a 084 engine, I would appreciate your input!
    Thanks,
    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

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    Re: General Prop Discussion

    Hey Buster, I also make my living by selling boats and parts. We never got to try the higher ratio drive on the 084. We only had the 1.89 to 1. The 60 inch 3 blade IVO was not enough prop for that ratio. I think it may be good for your higher ratio and would like you to try it. The cost is $ 600.00 plus shipping. If I sell it to you and it don't work good, you can send it back to me and i will apply your funds towards the cost of another prop. That makes it satisfaction garranteed. The only thing you would loose is the shipping cost. The 3 blade Warp Drive may be better but it cost $ 1135.00. With the 40 HP Kohler, we got the fastest speed with the IVO and the best ground push with the Warp Drive.
    Thanks, Chuck

  12. #12
    Senior Geezer buster's Avatar
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    Re: General Prop Discussion

    Chuck, I think you just made the sale. I would rather have more ground push, but $1135. sounds like an awful lot for my limited budget. I will be calling you very soon. Thanks,
    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  13. #13
    Senior Geezer buster's Avatar
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    Re: General Prop Discussion

    Hey Chuck,

    I now have the 084 started finally, with the 60 inch IVO prop mounted. I was reading through the instructions. I noticed they did not mention the maximum rpms recommended.

    Anyway I called IVO, and the fella I talked to claimed they do not have a max. rpm. Can that be correct? You would think there must be an upper limit!

    I don't think I will need to be concerned about it, with my reduction, and about 3600 rpm max. that I'll be running the 084, but I was just wondering

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

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    Re: General Prop Discussion

    You don't have to worry buster. A good safe point would be 3000 rpm. It could even be turned more but the proformance does not get any better.
    Thanks, Chuck

  15. #15
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Re: General Prop Discussion

    Buster,

    How'd you have the pitch set during your initial testing? I'm guessing it was pretty low, if you were able to run the engine up to 4000 RPM.

    I must agree with you that there HAS to be an upper limit on the IVO prop's RPM. I wonder why they didn't disclose that to you. But I bet that Chuck's 3000 RPM "good safe point" is really a good safe point. He has a lot of experience with these props.

    With the reduction drive, I'd think that if you start out with a high pitch to limit the engine to less than 3600 at WOT, and then carefully reduce the pitch from there, to slowly increase the engine to 3600 RPM, you'd be good to go.

    That's the strategy that I'm planning to use with my GSC prop anyway.

    Did the IVO prop bolt up directly to the Arrow Prop reduction? I've got an adapter to use the GSC prop (it has a Rotax pattern), but would prefer that it be a direct bolt up.

    I figured that I'll have to go thru at least a couple of props before I find what I want. For that reason, I wanted to start out with an adjustable pitch prop at first. I found this 66" 2 blade GSC prop with adpater for a good price, so that's what I bought for my 1st prop.

    Eventually, I plan to go with a 3 blade prop. From what I've read, odd numbered blades are quieter than even numbered. I don't know from personal experience, YET.

    But one of my objectives is to make my boat reasonably quiet.

    So, I'm all ears to see how your IVO prop works out.

    Thanks,

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  16. #16
    Administrator Papee's Avatar
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    Re: General Prop Discussion

    Keep in mind if you are using the stock carb that these motors were designed to run at a constant 3200 rpm. If you run more than that the carb will not be able to keep up. I have mine set up now that it runs 3200 rpm and I now longer run out of gas. Before if I ran over 3200 rpms it would run out and I would have to slow down so it could catch up. I'm not sure what rpm you could get away with with another carb on but they do run warmer if you go much higher than designed.
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  17. #17
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Re: General Prop Discussion

    Papee,

    Ummm.... didn't you INTEND to say they were designed to run at "3600" RPM?

    Respectfully submitted,

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  18. #18
    Administrator Papee's Avatar
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    Re: General Prop Discussion

    Yea I had 32 on the brain, that is what I have mine set at not what they originally ran.
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  19. #19
    Senior Geezer buster's Avatar
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    Re: General Prop Discussion

    Duane,

    That was a lot of questions for a guy with CRS to remember, but I'll try!

    The Arrowprop Reduction came with an adaptor for the IVO Prop. However, After I tried installing it using the bolts that came with the prop, I found out that they must have sent the wrong bolts. (The instructions state: Use only the hardware supplied with the prop.) Anyway, I thought they were turning hard, but I figured that was so they would not loosen in use! They also bottomed out before they tightened up. I broke two of them off, and was not able to remove them.

    Long story short, I ordered a new adaptor from Arrowprop and went to American Fastener, and they supplied the correct bolts.

    I just bolted the prop on and did not attempt to adjust pitch before starting it up. I have an electric fuel pump beside the tank, and even on three cylinders, I think it would have turned well past 4,000 if I would have tried.

    I can't tell you what the pitch was. My goal this time was to get the engine to run. After it runs right, I'll get around to adjusting prop pitch.

    When we started it up, the boat was sitting in the pole barn (shop) with the prop blowing out the big door. The noise (Edit: I meant - sound!) did not seem bad at all, although I don't have a decibal meter.

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  20. #20
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    Re: General Prop Discussion

    The Arrowprop adaptor has SAE threads and the IVO Prop is shipped with metric threads. I should have stated that in earlier post. Sorry.
    Chuck

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