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Thread: New Prop Needed..... Which one for new boat

  1. #1
    Member GrassLakeRon's Avatar
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    Default New Prop Needed..... Which one for new boat

    Hi all,

    I moved my 50hp Evinrude to my 18' Sylvan Sea Master. It is about 600 pounds heavier then my smokercraft. I currently have a 11 3/4 x 17 prop on it now (which is stock). It planes at 20 mph and tops out at 26 mph. What prop would I need to get a better hole shot and a couple more mph top end. I have no tach but it seems that the engine is running at a lower top end rpm. I was thinking a 13 pitch....... What would you recommend?

    Thanks

    Ron

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    Moderator stid2677's Avatar
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    Think or your prop, like a gear... The lower the pitch number the more torque. A lower pitch will give you a better hole shot,, but lower top end. A higher number and you get less hole shot and higher top end. Going from 17 to 13 is a lot of difference. One thing to consider is changing to a 4 bladed prop if you are running a 3 bladed.

    I run a 3 bladed 17 pitch on my Wolly and changed to a 4 bladed 15 this spring to have as a spare. The 4 bladed 15 gave the boat a much better hole shot but I lost about 7 mph on top end. However the 4 bladed gets way more weight on step and keeps it on plane at much lower speeds. The 4 bladed is much louder and causes more torque steer.

    I have heard that some composite props can help with both hole shot and top end as they flex on hole shot and straighten out as you get on step and allow for a better top end.

    Good Luck

    Steve
    "I refuse to let the things I can't do stop me from doing the things I can"
    Founding Member
    http://www.residenthuntersofalaska.org/

  3. #3
    Member GrassLakeRon's Avatar
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    Thanks. I have been looking at all the performance data from various websites on weight, hp and prop pitch. This is an area which I have never messed with.

  4. #4
    Supporting Member Old John's Avatar
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    Quote Originally Posted by GrassLakeRon View Post
    Hi all,

    I moved my 50hp Evinrude to my 18' Sylvan Sea Master. It is about 600 pounds heavier then my smokercraft. I currently have a 11 3/4 x 17 prop on it now (which is stock). It planes at 20 mph and tops out at 26 mph. What prop would I need to get a better hole shot and a couple more mph top end. I have no tach but it seems that the engine is running at a lower top end rpm. I was thinking a 13 pitch....... What would you recommend?

    Thanks

    Ron

    I agree with Stidd2677 To drop to a 15 pitch from a 17 would be much better than to change to a 13 from a 17. the 2" change in pitch will improve your hole shot, as would changing to a 4 blade vs a 3 blade. but in both instances you'll loose a little off the top end.

  5. #5
    Member GrassLakeRon's Avatar
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    So I guess based upon my findings, that the 17 isn't such a bad choice after all. If I went with a 15 then my top end and plane speed would get closer.
    "Equipped with his five senses, man explores the universe around him and calls the adventure science"

    Edwin Hubble

  6. #6

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    You can see some of that data at Piranha Props, I have used them for 15+ years, some good things like if you hit things they give, but flex more than metal! but there are charts that show pitch verses speed.

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