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Help Help Help!! 1979 236 Volvo AQAD40B

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  • Help Help Help!! 1979 236 Volvo AQAD40B

    Classic Mako!!!

    Hoping a few members can chime in on a good solution. I am running a 1979 236 mako inboard with a Volvo penta aqad40b. My velvet drive is 2 to 1 and I have been changing props left and right to find the magic prop.

    My first prop was a 4 blade 17 x 18 (cup unknown) which pushed the boat along at 17/18 mph @ 2800rpm and 24/25 mph WOT. A sand bar ended that prop, shaft etc.

    After some repairs, I ran an 18x17 4 blade (cup unknown) and my performance dropped drastically. I now cruise at 15/16 mph and WOT is 22/23 mph.

    Not satisfied with the slow boat, I called ACME and they sent a 18x20, which I caused the boat to blow a ton of black smoke and took awhile to get up on a plane. My WOT went to 25/26, but I lost 500rpm and my cruise at 2.800 rpm was 18/19.

    Sent it back to acme and against my wishes they wanted me to try a 18/17 to get back to max rpm. SO my performance numbers dropped back down to prop #2, which only cost $180 vs. the $1,000 from acme.

    At this point I am at a loss. I want to try and get the boat as fast as possible at cruise rpm and am hoping this number to be closer to 23/24/25 mph. Does anyone have any suggestions or run a similar rig?

    Thanks!

    Joe

  • #2
    While many of us would love to have a diesel 236 I dont believe many have had. Acme is a good prop building company, and if your engine is producing its advertised HP, they should be able to come up with a suitable configuration.
    [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

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    • #3
      How's the turbo? It might not be a prop issue.

      Also why a 2:1 and not a 1.5:1?

      You may not want to hear this, but you're probably underpowered.
      1975 Mako 26 Inboard[br]1976 Mako 23 Inboard[br]1984 Rhodes 19[br]Padanaram, MA

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      • #4
        Yeah the Acme props are unbelievable. The cost to ship back and forth is annoying. But hey, I guess it comes with the territory of owning a boat.

        And yes, I do think I am underpowered a bit. I think a Cummings 6bta 330 or 370 has the same footprint. I fish out of fire island and am trying to get into these bluefin as they migrate in spring and fall I was out 35 miles and felt ok, just wish she was a little faster. With that said, love th 236, just don't know if it's realistic to make those types of runs in a 23'. Trying to see if I should cut it loose or restore completely.

        Trans was in it when I bought it

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        • #5
          Yeah the Acme props are unbelievable. The cost to ship back and forth is annoying. But hey, I guess it comes with the territory of owning a boat.

          And yes, I do think I am underpowered a bit. I think a Cummings 6bta 330 or 370 has the same footprint. I fish out of fire island and am trying to get into these bluefin as they migrate in spring and fall I was out 35 miles and felt ok, just wish she was a little faster. With that said, love th 236, just don't know if it's realistic to make those types of runs in a 23'. Trying to see if I should cut it loose or restore completely.

          Trans was in it when I bought it

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          • #6
            quote:


            Originally posted by 2mehouse


            Yeah the Acme props are unbelievable. The cost to ship back and forth is annoying. But hey, I guess it comes with the territory of owning a boat.


            And yes, I do think I am underpowered a bit. I think a Cummings 6bta 330 or 370 has the same footprint. I fish out of fire island and am trying to get into these bluefin as they migrate in spring and fall I was out 35 miles and felt ok, just wish she was a little faster. With that said, love th 236, just don't know if it's realistic to make those types of runs in a 23'. Trying to see if I should cut it loose or restore completely.

            Trans was in it when I bought it


            35 miles each way? Drop a Chevy EFI 350 in it and call it a day. I've done well over 80 in a single trip and had plenty of fuel left.
            1975 Mako 26 Inboard[br]1976 Mako 23 Inboard[br]1984 Rhodes 19[br]Padanaram, MA

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            • #7
              You have a great boat/engine combo.

              But its not a speed demon. Even with a 350ci gas engine these boats top out at 28-30 best case.

              That Volvo is probably on the lower part of the power curve for that hull. But it will absolutely run all day every day in low 20s.

              There is a 236 for sale right now in Texas that has a fresh rebuilt 6bt and I think he only gets 30 at top end.

              The 236 is one of best of the classic makos. The diesels versions are few and far between. If you want something faster, get a mako 25 and put twin 200 2 strokes. That should push 40-45. But the reliability factor will be an order of magnitude less. A mako 25 with a single 300 four stroke will increase reliability a little over the 2 strokes and get you low 40s

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