Problem With New Motor On Tritoon

Discussion in 'Outboards' started by marktime53, May 11, 2014.

  1. marktime53
    Joined: May 2014
    Posts: 3
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    Location: South Carolina

    marktime53 New Member

    Hi All,

    I have a 2003 Triton Summit Platinum 250T (25 ft. tritoon with lifting strakes) that came with a 2003 Mercury 225 EFI, 20 inch shaft and 1.75:1 gear ratio with a 17 pitch Mirage Plus prop (3 blade). This configuration was very good and hole shots were not a problem and at WOT (5500 5pm) she would run about 53 mph.

    I replaced the motor with 2014 Mercury 225 Optimax Pro XS and I am having problems with the boat "plowing" water; lots of water splashing/displacement occurring between the toons. Optimax is same shaft length and gear ratio, but actually is 247 horsepower. It appears that the rear end of the boat is not levelling out with the surface of the water. I have tried my old 17 pitch prop, and a 19 pitch prop, both of which generated 6100 rpms WOT. I also tried a 21 inch prop and maxed out at 5800 rpms. All tested props are 3 blade props. Getting alot of water displacement REGARDLESS of motor depth setting/prop used. Cavitation plate is exposed on some of the settings, but still getting the water displacement/low maximum speed.

    My maximum speed was 46 mph with the 19 pitch prop at one hole setting above the last hole (3/4 inch from maximum depth placement of motor). I Have tried every motor height setting with these three props and the results are basically the same. I am considering a manual jack plate that would move the motor back 4 inches from the transom, to help with planing the rear of the boat out. In addition, the Optimax weighs 20 pounds more than the EFI did per Mercury.

    I have read the hydraulic jack plates and the 8 and 10 manual jack plates place alot of stress on the transom but I would consider this option if necessary after I ahd a welder reinforce the transom. Any and all suggestions would be welcome.

    Thank you for your time,
    Mark
     
  2. powerabout
    Joined: Nov 2007
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    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    your not mentioning angle of trim in this conversation?
     
  3. marktime53
    Joined: May 2014
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    Location: South Carolina

    marktime53 New Member

    trim

    I started at trimmed all the way in for getting out of the hole and trimmed motor til it began to blow out, I did this on every test, no significant change despite motor height, little or no change in low, mid or wot speed.
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Doesn't make much sense, you say you got out to 6100rpm with a 19 inch prop on your new motor, but only achieved 46 mph, yet with a 17" pitch prop you made 53 mph @ 5500 rpm on the old engine ? I do not understand.
     
  5. marktime53
    Joined: May 2014
    Posts: 3
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    Location: South Carolina

    marktime53 New Member

    Tritoon

    Neither do I, thus the posting on the forum here.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Well, in theory, it can't happen. Even if you have increased the weight of the boat drastically, it would be slow to plane and top speed lower, but it would not be reaching those revs, it does not add up.
     

  7. slow fred
    Joined: Feb 2011
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    Location: florida

    slow fred Junior Member

    Are you checking the speed with a GPS ?
     
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