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Which prop for Mercruiser 350 Mag

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  • Which prop for Mercruiser 350 Mag

    2003 Caravelle 207 (open bow runabout)
    2900 lbs dry
    350 Mercruiser MPI mag 5.7L 300 HP (100% stock)
    Bravo 1 (1.5 ratio)

    Props tried
    Cheapo aluminum 4 blade Solas 14.25 x 19: 53 MPH @ 5000-5200 RPM
    4 blade stainless 14 x 23: 50 MPH @ 4000-4200

    The Mercury prop calculator recommends the following. Can anyone speak from experience on a boat with a 350 Mag of this weight and hull configuration which prop would be the best? The performance goal is 60 MPH. I don't even need to stick with a Mercury prop if something else out there is better/optimum.
    Last edited by 40Coupe; September 25th, 2017, 10:30 PM.

  • #2
    Here are the props recommended by the calculator using the data from my existing two props.

    Enertia® X7 Alloy 3 13.8 20 RH 899000A46
    Enertia® X7 Alloy 3 13.6 21 RH 899002A46 - This is the one I'm thinking about.
    Enertia® ECO X7 Alloy 3 16 19 RH 8M0040400
    Laser II Stainless Steel 3 14 19 RH 16544A46
    Mirage® Plus Stainless Steel 3 15.25 19 RH 13700A46
    Revolution 4® Stainless Steel 4 14.625 19 RH 857026A46
    SpitFire® Mercalloy 4 14 19 RH 8M0084495
    Vengeance® Stainless Steel 3 14 19 RH 16316A46
    Vensura® Stainless Steel 4 14 19 RH 825900A48

    Something tells me a little smaller diameter is going to let the boat RPM better, 3 blades for less drag a bit more pitch to bring that MPH up. Let me know if my thinking is off. I really don't want to buy 4 different props to get it right. But I'll do what I have to do to get 60.


    • #3
      The Enertia is a great prop, been running one since 2006. A 21 or 22 would probably the best choices. I did vent the prop using the medium size vent plugs


      • #4
        X2 for Enertia in a 21 or 22" pitch. I've run both the enertia and the vensura on my boat. Enertia will do much better for top end.


        • #5
          If my recollection is correct, the prop on my Bravo 1 is a 17" Mirage Plus connected to my 350 Mag MPI. I know it is a 17" but fuzzy if it is a Mirage Plus but am like 80% sure but the Mirage Plus was technically for big blocks not small blocks so is a lot of prop for a small block. It's great for out of the hole performance as my boat is about 800lbs heavier dry than your weight. Top end completely loaded with 60 gallons of gas and as many people as I want is 53mph but is almost exactly 5000 rpm's indicating the prop is too much for this engine or it would be overrevving like crazy. It is the worst prop I've ever experienced for blowing out in turns though. Circling around to pick up a fallen boarder is an exercise in widening the turn and slowing way down or it will blow out. My boat's official published boat test back when it was in production was with a B3 not a B1 and was right about 60mph gps and a few clicks higher with radar and mid 60's on speedo. Not sure what prop I'd need to get to that magical 60mph on GPS.
          2002 Chaparral 220 SSi
          350 MAG MPI
          Bravo 1

          2011 Yamaha FX Sho


          • #6
            Thanks! Any options on the 13.6 to 13.8 diameter? Will the smaller prop diameter be a good move?


            • #7
              In a lot of prop lines, as pitch increases diameter decreases. Why? Let the prop engineers worry about it


              • #8
                Keep hearing the enertia is superb...santa has his order for mine !
                Can also recommend a laser 2. Can't go too much wrong with one and a useful and appreciating asset to any boat owner.
                I also have a ballistic, but it's luck of the draw to get it dialled in right consitantly.
                Laser 2 is the best all round to date.

                Just on your details...keep an eye on those revs. Max is 5000 rpm. You might even find that a good 19" would have the revs spot on, if you getting 5000-5200 with a cheapo ally 19".
                Your boat seems to be light for its size. Mine is only 18ft, but over 3000 lbs dry. I run a 19" for best all round.
                If you are able to try different props out and knowing what I know from trying different props...I'd go straight for an enertia 19" and perhaps slightly higher. They do 1" increments in that prop. 20" would sound ideal at an educated guess.


                • #9
                  Great advice!


                  • #10
                    [QUOTE=QBhoy;n10491859]Keep hearing the enertia is superb...santa has his order for mine !QUOTE]

                    Santa better be good to the wife too... Or you are in the doghouse


                    • #11
                      Originally posted by QBhoy View Post
                      Keep hearing the enertia is superb...santa has his order for mine !QUOTE]

                      Santa better be good to the wife too... Or you are in the doghouse
                      Haha Jimmbo....a pair of Jimmy Choos shoes has been mentioned and are incredibly similarly priced !
                      I'm thinking that since you are largely responsible for my requirement for this enertia....you should do what's right...and source a pair across in the US (cheaper there) and at the very least half in for them !
                      Thanks in advance Jimmbo ! Haha.


                      • #12
                        Jimmbo....out of interest and given the flexibility of the 1" pitch options of the enertia...I'm a bit unsure of whether to stick to the same pitch as the laser, ballistic etc or what.
                        When going from another stainless example to your enertia...what did you find ? Did you gain revs or what given the same pitch ? If I have it spot on with the laser, should I stick to that pitch or will I see a gain or loss in revs, given the thinner blades and lighter design ?


                        • #13
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                          I used to run a 20 RAKER. Sheez that was 11 yrs ago. They were within 50 rpms of each other at any given speed with the Enertia being the lower revving prop. I felt the Enteria had a slightly better grip on the water, not that the RAKER was a slouch. I can't comment on Laser or Mirage, Ballistic, or other as I never ran them on the I/O. The 20 Raker gave me the same rpm as the 21 AL VP prop that came with the boat, but more speed. The entire boat, not just the bow, rode higher in the water.
                          I did run a Ballistic, a Viper, and a Stiletto on my OB back in 1999. There I could say the Stiletto was similar to the RAKER, but the Ballistic didn't do anything special. As always YMMV.
                          I have been very fortunate when it come to trying out props. My dealer let me try the Enertia off of his personal boat. Then sold me mine at cost(actually lost money after the CC charges were applied) In the past he also lent me the Stiletto, a RAKER, a Viper, and various other props to try. I did put the Viper on the rocks, but since it was a used prop, and the Dealer had a customer that wanted a test ride in a boat he was looking at, we settled by me taking the potential customer out in my boat.