Merc 115 4st. CT prop

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  • Merc 115 4st. CT prop

    Hi. I've been searching for Stainless Steel prop info for this motor for some time now. I have a 2016 Magnitude Aftershock 18 foot welded aluminum boat with windshield that probably has a dry weight of around 1100 lbs. Add in the 2016 Merc 115 4st. CT and all the other gear and I'm guessing I have a total weight of about 2300 lbs. The boat has a very open floorplan with no carpet, storage, etc. Only a driver and passenger seat behind the windshield. I have used the following props;
    14.25 x 21 black max. 3 blade aluminum. WOT= 42 mph @ 6200 RPM [not hitting rev limiter]
    14.25 x 21 turning point hustler. 3 blade aluminum. WOT= 42 mph @ 6000 RPM 14 x 23 black max 3 blade which blew out so bad I took it right off the motor.
    I have a great hole shot with either 14.25 prop and the boat planes out effortlessly. The black max will cavitate if I trim up too much at speeds and will loose traction easily when cornering. The turning point will take much more trim and hold corners much better. Both props seem to have a lot of slip.
    Mercury prop finder thinks I could run a Tempest plus at a 14.6 diameter in 21 p. I'm thinking a 14.5 diameter in 21p. would be a big jump and hurt the RPM's. I have no experience with SS props. Will they spin up easier thus allowing a WOT of 6000 rpm ?
    Please advise with your results.
    Thank you.
    Mark

  • #2
    Tempest 21 will be the one to try.
    one of two things will happen, you'll gain speed and get the RPM.
    or you'll top out at 42 MPH and drop the RPM.

    If you email me that you want to run the 21 Tempest Plus, I'll let you know when I get mine back. I send them out for $30 plus shipping.

    Ken Reeves
    [email protected]
    941-735-5808

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    • #3
      Email sent to Ken.
      Will post results when available.
      Thank you

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      • #4
        UPDATE; Finally, the wind died down and I got a chance to go run the Tempest plus 14.625 x 21. I gained 2 mph, up to 44 mph now. Max RPM went down to 5800. Hole shot is still excellent and I have all the bow lift I'll ever need. I also installed the mercury vessel view mobile to verify that my dash analog gauge is accurate. I went from slip in the high teens with the aluminum props to 9% with the S.S. prop. Think I'll leave it on and call it good. Max GPH at full throttle= 10.8... GPH @ 27 mph is 3.8
        Thanks Ken
        Mark

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        • #5
          Nice !! thanks for following up with the numbers !

          Ken Reeves
          [email protected]
          941-735-5808

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