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  • #46
    Thanks Steve!
    Karen
    Punxsutawney, Pennsylvania
    1986 Shamrock H/T with RWC 330 hp PCM, dual hydraulic helm
    1992 Mako 211CC w/Mercury Optimax 175
    3 other smaller OB boats and a trusty old canoe...

    Comment


    • tuner
      tuner commented
      Editing a comment
      You are welcome, I'm happy to contribute when I can!

  • #47
    Let's make this interesting. Jerry, I formally challenge you to a drag race at the next get together.
    1980 pilot house 351
    1988 260 predator 408

    Comment


    • #48
      I'll drop the starter flag!

      winner gets cheesecake with choice of toppings!
      Karen
      Punxsutawney, Pennsylvania
      1986 Shamrock H/T with RWC 330 hp PCM, dual hydraulic helm
      1992 Mako 211CC w/Mercury Optimax 175
      3 other smaller OB boats and a trusty old canoe...

      Comment


      • #49
        Now I'm thinking turbo.
        1988 26' cuddy
        1975 20' open
        16' Sandpiper
        14' Certified Fiberglass

        Comment


      • #50
        Might need to Jerry, I know Steve was beefing his up pretty good....
        Karen
        Punxsutawney, Pennsylvania
        1986 Shamrock H/T with RWC 330 hp PCM, dual hydraulic helm
        1992 Mako 211CC w/Mercury Optimax 175
        3 other smaller OB boats and a trusty old canoe...

        Comment


        • #51
          Dave, Karen, Tuner, what prop are you using?
          1988 26' cuddy
          1975 20' open
          16' Sandpiper
          14' Certified Fiberglass

          Comment


          • #52
            I’m running a 16x15.5 with a 6 cup.3 blade. Eastern Propeller Built me a couple of them once we landed on that. I can send you the specs if you want to have your prop guy duplicate it. I can send you one of mine that’s already done if you want to try it first.

            Comment


            • #53
              I started with a 16x17 6 cup and couldn’t hit wot. I think it was around 4300. The boat ran great at 3800 rpm and had great speed. I would imagine I could have ran it that way indefinitely but I wanted to be at the low end of wot rpm.

              Comment


              • #54
                Acme 2275 15x15.75 4 blade. The gear is 1.5:1. My top speed in ideal conditions is 35-36mph.
                Steve
                1998 260 Mackinaw Sea Maxx 5.7 HO TBI 12' Klamath w/ 20hp Tohatsu EFI

                Comment


                • #55
                  I made a big mistake going with the 1.91:1 transmission and 17" RH 4-blade behind my Mercruiser 383 MAG MPI (rated max 350 HP / max 390 ft. lbs.). I'm getting fairly poor fuel economy with it (about 1.40 NMPG/1.6 SMPG). I'm reaching 4930 RPMs @ WOT doing about 28.5 knots (32.8 MPH) with just me and full fuel tanks. I'm getting about 4800 RPMs at WOT fulling loaded down with full fuel tanks, the 3 of use, a 48 gallon bait tank running, 140 lbs. of ice, and gear. Therefore, I'm under-propped some with the 17" x 15.5" 4-blade, which probably explains my somewhat poor performance at cruising RPMs (about 18 knots between 3400-3500 RPMs in open ocean loaded down). Adding 1" of pitch may give me the cruising speed I'm looking for, but it will not likely be enough to reach my desired fuel economy. I recently got a killer deal on a rebuilt 72C 1.52:1 transmission ($400). So I plan to swap out the current one with this, and install a 16 x 15 3-blade. I'm confident that I'll get better performance numbers with this setup.

                  Stick with the 1.52:1 and go with the appropriate prop. Staying within the parameters that Steve mentioned above for the cam is key. Anything over 600 CFM carb with the 383 would be over kill IMHO. Adding the AFR 185 heads will push you over the line in what you are looking for performance wise in my opinion!

                  I'm anxious to hear the performance on your new build! Please provide all the details on dyno results, cam specs, heads, carb, prop, etc.
                  1990 Shamrock Mackinaw
                  Mercruiser 383 Stroker MPI
                  VD 72C 1.91:1/ACME 17x15.5 w/.075 cup 4B

                  Comment


                  • #56
                    My engine builder has not even started on my engine. I have a few props and gears. My plan is to stay with my 1:5 - 1 and a 16 x 15 3 blade. That is what I had when the stroker was in the boat before.
                    1988 26' cuddy
                    1975 20' open
                    16' Sandpiper
                    14' Certified Fiberglass

                    Comment


                    • #57
                      I loved my Mack, I really did. But I don't believe it was built for speed. Just a solid platform that ran through anything you put in front of her. I never ran her hard and I was happy with what she put out. Generally around 18 knots is what I liked.
                      Jeff
                      2008 32' Carolina Classic
                      1990 Shamrock Mackinaw (sold)
                      1998 Shamrock Pilot (Sold)

                      Comment


                      • #58
                        I hear ya Rod but cruising at 23 knots would really make me happy.
                        1988 26' cuddy
                        1975 20' open
                        16' Sandpiper
                        14' Certified Fiberglass

                        Comment


                        • #59
                          Yeah 23 to 25 is nice in the Pacific. Since I sold the Mack, I bought a 32' Carolina Classic that just scoots!
                          Jeff
                          2008 32' Carolina Classic
                          1990 Shamrock Mackinaw (sold)
                          1998 Shamrock Pilot (Sold)

                          Comment


                          • #60
                            Rod, tell us about the Carolina Classic. Diesels? I assume twins. Whole different game with a boat that big. Dock space, maintenance, hauling fees, etc. Main reason I sold the 31 was the lack of dockage around here and the depth of the inlet. Sure did like the 25 MPH cruise and the comfort. Ease of engine access. Not crazy about the fuel burn but I knew it going in.
                            1988 26' cuddy
                            1975 20' open
                            16' Sandpiper
                            14' Certified Fiberglass

                            Comment

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