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1860 prop selection

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  • 1860 prop selection

    Hey guys....running a 2015 Alumacraft 1860 MV Jon w a 2015 Mercury 50 4 stroke. Right now I'm running a 12p aluminum and also have an 11p stainless. Motor came w a 15p, but wasn't even close to the RPMs it needed to be so i dropped to a 12p. I'm seeing about 27-28mph w 2 guys going up river, and 31-32 coming down.
    A friend of mine bought an 1860 Grizzly and is seeing 41mph w 3 ppl, Im unsure of what he's running for a prop, but I'm guessing it's got to be substantially more pitch than my 12???

    Any thoughts??????

  • #2
    Might have substantially more HP too

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    • #3
      Originally posted by jimmbo View Post
      Might have substantially more HP too
      Hes running a 50hp Merc as well.

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      • #4
        41 mph on a 19 footer doesn't sound likely with a 50hp. 41km/hr perhaps

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        • #5
          Assuming that's ~625# dry weight boat. Remove the air intake restricter to increase hp and then use the 15p prop. You should see ~ 40 mph at 5500 rpm with one person. Make sure the engine is mounted at the correct height first.
          https://www.mercurymarine.com/en/us/...or/#!/step-one

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          • #6
            I thought 41mph seemed awful fast as well, esp w 3 passengers. I do have a 15p laying around that I may try out, I need to get a tach on it and see what I'm running for rpms....
            Wes, what height are you recommending?? I'm also running a Micro Jacker on it as well.

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            • #7
              Was your friends boat using gps or the dreamometer on the dash ? Unless he has a jack plate and some serious set up....it seems very ambitious. Maybe he does ?

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              • #8
                Originally posted by flex2win View Post
                I thought 41mph seemed awful fast as well, esp w 3 passengers. I do have a 15p laying around that I may try out, I need to get a tach on it and see what I'm running for rpms....
                Wes, what height are you recommending?? I'm also running a Micro Jacker on it as well.
                What is your Engine WOT RPM range, and what are you getting?
                At speeds below 45 miles an hour the the engine height isn't too critical. You have a Tin boat, does it have a pronounced Keel? If so, and it doesn't taper off 3 ft or so before the transom, you will have to keep that in mind when choosing engine height. At speeds up to 30mph, having the Anit-Ventilation Plate between 1" below the the hull/keel and flush/even is fine. From 30 to 50 mph. flush is usually the standard. From 45 mph and up higher heights are sometimes doable. A lot will depend on your prop. Some High Performance Props run very well partially submerged. There is no free Ride, Higher heights can have a price, Ventilation on Acceleration(usually worst just before getting on Plane), and turns. Less ability to trim the bow up or down. At higher heights the is the risk of staving the engine of cooling water.

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                • #9
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                  Originally posted by flex2win View Post
                  I thought 41mph seemed awful fast as well, esp w 3 passengers. I do have a 15p laying around that I may try out, I need to get a tach on it and see what I'm running for rpms....
                  Wes, what height are you recommending?? I'm also running a Micro Jacker on it as well.
                  Depends on the hull. If you have a center keel Like I do on my oat, then about 2 inches above it Water is 780 times the density of air, so the drag matters at any speed. If you don't have a keel and the hull is flat at the back, then ~ a half inch above is good. If you have a setback plate, then raise it ~another inch for ever y 2 inches of setback. Here's a photo of mine fore reference.
                  Click image for larger version

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