Contender 25 Prop Help

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  • Contender 25 Prop Help

    hello there, I have a 1994 25 contender same as the newer competition 25 hull that I have been restoring. The boat currently has twin 2005 Merc 150 efi 2 stroke motors with Mirage Plus 17P props. Despite good overall performance at lower speeds, with 3/4 of a tank and two people on board I can only get to 4300 rpm at 38 mph at WOT. From my understanding these motors rev to 5-5.6k rpms and these hulls typically get close to 50mph top end out of 300 hp. Does this sound like the correct props for this application? maybe I need to look into something else? Would really appreciate your feedback and expertise as I would ideally like to cruise in the 30mph range and have a mid to high 40 mph boat. thanks

  • #2
    Both motors getting the same RPM at wide open?
    Where do you have the tabs, when running wide open? Are you trimming the motors up much? what happens if you trim higher?
    What holes are the motors mounted in?
    Bottom of the boat clean, no growth, or if painted, its in decent shape?
    100% thats 38 MPH and not KTS ?
    How much fuel, gear, people, on the boat for that 38 MPH run?
    By chance, do you know your GPH at wide open?

    Ken Reeves


    • #3
      The starboard motor is off by about 100 rpm that I usually compensate for with the throttle. I believe that is caused by the boarding ladder that was mounted by the previous owner under the bracket that may be causing a small amount of drag. It can easily be taken off.
      Otherwise, the hull bottom is very clean and has never been bottom painted. For Yesterdays test drive I kept the trim tabs aligned with the running surface of the boat and did play with the trim of the motors. I basically trimmed up until the boat began to porpoise then I dropped down slightly until it was corrected. This is where I got the 4300 rpm at 38 mph. I did double check that the gps was reading in mph and not in knots.
      This was only the second time we've taken the boat out since purchasing so we kept the boat relatively light with about 110 gallons of fuel plus my father and I. No other heavy gear just safety equipment. I do believe the motors are mounted low as the highest mount on the engine bracket is mounted in line with the highest mount on the stainless marine bracket.
      Is that enough to take away that much rpm and top speed?
      I do not know what the gallon per hour was sorry.
      once again thank you for your help.


      • #4
        Well, maybe take a look at the engine height while your running.
        here is a link with some pictures of what to look for.

        Wondering if the throttle linkage is set correctly and your actually getting full throttle or not. (that is why I was curious on the GPH at wide open.

        I would expect that boat to run mid 40's pretty easily.
        "IF" you could turn 17 pitch Mirage Plus props 5600 RPM, I'd expect you'd be running mid to high 40's.

        Ken Reeves


        • #5
          Here's a little update, although I will be raising the motors shortly bc I still believe they are sitting a bit too low according to that link, we found that we were having fuel pressure issues and one of the engines had a bad coil. After solving those problems we were able to get up to 48 mph with three people and half tank of gas using the same mirage props. Im very pleased with those numbers.


          • #6
            Nice !

            Ken Reeves