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Thread: What prop size?

  1. #1
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    Default What prop size?

    I'm thinking about trying a different prop to try and pick up some more speed. I have a 17 pitch 4 blade Solas on a 60hp Mercury command thrust, boat is a 1656 Havoc marsh runner with a vance kick and jack. Right now I'm getting 42 mph empty and 38mph loaded with 2 people. I have the bigfoot that has the same hub size as a 115hp if that makes a difference.

    What does the brain trust suggest?

  2. #2
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    Drop down a pitch. If you get it right there shouldnt be much difference between empty and loaded id say you are close

    Caveat is i like boats with low end torque. Jump on plane. Not worried about hauling butt and racing.
    "Eventually, all things merge into one, and a river runs through it. The river was cut by the world's great flood and runs over rocks from the basement of time. On some of the rocks are timeless raindrops. Under the rocks are the words, and some of the words are theirs.
    I am haunted by waters" Norman Maclean.

  3. #3
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    4 blade is gonna be a hair slower usually too but hold in turns etc. 3 blade gonna be faster 4 blade drop a pitch. Ideally need a tach to tell. Empty you should be in 5600rpm and loaded shouldnt drop you but 100-200rpm.
    "Eventually, all things merge into one, and a river runs through it. The river was cut by the world's great flood and runs over rocks from the basement of time. On some of the rocks are timeless raindrops. Under the rocks are the words, and some of the words are theirs.
    I am haunted by waters" Norman Maclean.

  4. #4
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    Sounds like a 16 3 blade might be what I need. I had this same motor on a 1648 war eagle and it would flat jump out the hole and ran 37 empty. The Havoc is slower out the hole but faster top end.

  5. #5
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    We will need to know your current RPMs and current prop model to really know.
    Usually flat bottom boats like a bow lifting prop.

    As said above a 3 blade will get more speed than a 4. You want to increase pitch going from 4 to 3.

  6. #6
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    You can buy a tiny tach for less than $20. Like others have said, it is the only real way to do it. What was not mentioned is aluminum versus stainless. Aluminum will give you higher rpm because of its weight but obviously, its durability is why most prefer stainless. There are resources all over the internet specific to each engine that show ideal WOT rpms for proper prop selection. Google that bitch, seriously it is very helpful because not all want 5,600 rpms. MG
    Dum Spiro Spero

  7. #7
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    Aluminum will also deflect under load and cannot be made to the same geometries as a stainless prop.

  8. #8
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    15 spline 17p yamaha black stainless. Close thread.
    "Hunt today to kill tomorrow." - Ron Jolly

  9. #9
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    Quote Originally Posted by tman View Post
    15 spline 17p yamaha black stainless. Close thread.
    this......

    Ive got the same boat, with a built 2stroke merc, so I've got the smaller gear case. 16p black stainless is pretty hard to beat for an all around prop on my setup. good top end but still gets out the hole quick.

    The marsh runners were built to run the 4stroke mercurys. All the testing was done with 60 4stroke with a 16p black stainless with the smaller gearcase.
    Last edited by dixiedeerslaya; 09-27-2021 at 07:07 AM.

  10. #10
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    Quote Originally Posted by dixiedeerslaya View Post
    this......

    Ive got the same boat, with a built 2stroke merc, so I've got the smaller gear case. 16p black stainless is pretty hard to beat for an all around prop on my setup. good top end but still gets out the hole quick.

    The marsh runners were built to run the 4stroke mercurys. All the testing was done with 60 4stroke with a 16p black stainless with the smaller gearcase.
    I assume the larger gear case that I have is going to be slower overall than the smaller gear case 60 havoc tested with?

    I'll see if I can find a 16 or 17 black stainless to try out.

  11. #11
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    Yes Bigfoot gear case will be slower. Bigfoot was designed for a different application.

    Look up the Chinese knockoff of the YBS. I own two. They are exactly the same and I saved a lot of money.

  12. #12
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    Quote Originally Posted by Coastal Woodie View Post
    I assume the larger gear case that I have is going to be slower overall than the smaller gear case 60 havoc tested with?

    I'll see if I can find a 16 or 17 black stainless to try out.
    the larger gearcase opens the door for other larger diameter/pitch props as well.

    Quote Originally Posted by FULLCHOKE View Post
    Yes Bigfoot gear case will be slower. Bigfoot was designed for a different application.

    Look up the Chinese knockoff of the YBS. I own two. They are exactly the same and I saved a lot of money.
    yep, I'm not sure if they are making 15spline in the ching chong knockoffs, but if they are, I would go that route. The yamaha brand will run you 450+. The knock offs are about half that or less, and from what ive been hearing, they are about 95% of the performance of the yamaha brand.

  13. #13
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    Quote Originally Posted by dixiedeerslaya View Post
    the larger gearcase opens the door for other larger diameter/pitch props as well.



    yep, I'm not sure if they are making 15spline in the ching chong knockoffs, but if they are, I would go that route. The yamaha brand will run you 450+. The knock offs are about half that or less, and from what ive been hearing, they are about 95% of the performance of the yamaha brand.
    I really like this motor so if I'm losing some speed with the larger gear case that's no big deal. I'd just like to squeeze about 45mph out of it if I can. I didn't even realize I had the bigfoot until I swapped props with my dads 115 pro xs one day.

  14. #14
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    Quote Originally Posted by FULLCHOKE View Post
    Yes Bigfoot gear case will be slower. Bigfoot was designed for a different application.

    Look up the Chinese knockoff of the YBS. I own two. They are exactly the same and I saved a lot of money.
    Thanks, I'll look into those as well.

  15. #15
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    My old 60 Merc was a Bigfoot. I went down that road trying to find a different lower. From my experience and research it was only going to give me a couple extra mph. Splitting hairs. I found a nice stainless prop for it and called it a day.

    Good luck. I really liked my Bigfoot though, it pushed a heavy load very well.

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