3 Blade to 4 Blade Swap

Discussion in 'Prop Shop' started by buoy37, May 1, 2012.

  1. buoy37

    buoy37 I Love microskiff.com!

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    We have a small 15 foot boat that (in my opinion) takes way to long to get up on plane. After it gets on plane, it starts to porpoise. The motor is a new 30 horse ETEC with a 3 blade 10x12P stainless prop. Should I exercise all of my options with a 3 blade before switching to a 4 blade. Moving fast is not priority. Getting up on plane at a low RPM is.
     
  2. Brett

    Brett > PRO STAFF <

    Move weight forward...too much weight aft is making the boat squat on take off.
    I don't think the prop is too blame. Try jumping on plane with a passenger forward.
    See if that makes a difference.
     

  3. buoy37

    buoy37 I Love microskiff.com!

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    I don't have much else I could move forward. The battery is under the center console. The trolling motor and fuel tank are in the front.

    I will be removing the CMC jack plate and switching to a Atlas Micro Jacker to decrease rear weight.

    Here is the boat http://www.microskiff.com/cgi-bin/yabb2/YaBB.pl?num=1321761903
     
  4. Brett

    Brett > PRO STAFF <

    I'm guessing everyone sits on the rear deck when running.
    All that weight is putting the hull so out of balance that it
    can't get over the hump of water it's creating. Get someone
    up front to hold the bow down until on plane.
    Trim tabs will help, but hull balance fore/aft is the real trick.
     
  5. fsae99

    fsae99 I Love microskiff.com!

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    Does it take too long to plane with 1 person on board? Does it porpoise through the entire trim range? Does it porpoise through the entire throttle range? What RPM to you get at WOT?

    Does it have a pad on that hull, from the pictures it looks like it is flat in the middle with a little rise to the sides?
     
  6. buoy37

    buoy37 I Love microskiff.com!

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    All great questions. I will have to put the boat in the water Sunday to get them all answered.

    I have played with trim and JP to try and minimize the porpoising, but no luck.
     
  7. Creek Runner

    Creek Runner Well-Known Member

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    Take the jack plate off the boat completly, it's not needed. Mount the motor on the transom 1-2 holes up. As mentioned by carolina Jim, I'm wondering weather or not the boat porpoise at WOT.