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  1. #1
    Member
    Join Date
    Jan 2016
    Location
    Texas
    Posts
    762

    School me on vent holes. New Rx4 for Evinrude G2

    I just got a spare prop for my Evinrude G2 (250hp) on the back of my 2017 Ranger Z521c. The boat originally came with a 3-blade Raker HO (14.5 by 26 I think). Now I put on a 4-blade Rx4 (15 by 25p).

    There are adjustable vents in both props. My hole shot is great and I honestly don't care about hole shot. I am interested in top end speed. Can someone tell me how the vents affect this and if I should open or close them, etc?

    I have also read other folks talk about "blow out". Can someone explain this terminology to me?

  2. Member
    Join Date
    Jun 2004
    Location
    Murrieta, Ca
    Posts
    1,419
    #2
    The vents will not change top end at all

  3. Banned
    Join Date
    Aug 2011
    Location
    Boerne & Three Rivers, Texas
    Posts
    18,061
    #3
    Quote Originally Posted by plki View Post
    The vents will not change top end at all
    What he said. You would know what blowout was if you were experiencing it, basically upon throttle your motor over revs and your boat just sits there with your prop spinning away.

  4. Member
    Join Date
    Jan 2016
    Location
    Texas
    Posts
    762
    #4
    Good info, thanks guys. What differences do most see going from a 3-blade to a 4-blade prop? I realize this is generalized info and I don't know my prop-to-pad, etc.

  5. Member
    Join Date
    Jan 2005
    Location
    Red Oak Va.
    Posts
    10,597
    #5
    If the props turn the same rpm's you should run faster with the three blade 26" Raker II than with the four blade 25" Rx4. The fourth blade costs you 100 to 150 rpm's to turn so a 25 4 blade should turn about the same rpm's as the 26" three blade but the Raker being a higher pitch should be faster.