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Proper bolt holes for bigger motor?

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  • Proper bolt holes for bigger motor?

    The DT140 pushes the 17 to 41mph by GPS in glassy water, and throws two big rooster tails out either side. I can only guess that the bottom of the trim bracket is too low and that I have to move the motor up at least one set of holes (it's now as low as possible).

    How do I know how high it needs to go on the transom???

    HELP!
    \'72 Mako 17, Suzuki 140 FOR SALE[br]\'74 Mako 19B Project FOR SALE[br]Seabird 21 Project FOR SALE[br]San Juan 28 sailboat [br]Wake, VA[br][IMG]

  • #2
    Move it up one hole and run it again. Trim the motor for max speed and see if it will try to cavitate in a hard turn. If not you may need to move it up one more hole. Look at the spray too. If it doesn't have that spray and it doesn't cavitate in the turn with it trimmed up then your on the mark.

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    • #3
      The 1987 Mako manual states a 17' with 140hp should run 42 mph. Granted your boat is a few year older and every motor is not the exact hp advertised or on the deacal on the cowel. I expect you are within range. I read somewhere in a boating magazine (and I wish I could remember where) that engines manufactures are allowed a 10% variance in the rating on the way hp is certified. There is also the issue of where the rating of your motor is measured, powerhead or prop. You can have in dynoed to find out that the real number is.

      For speed you want the motor mounted higher to almost ventilate the prop on plane, but in turns it will cavitate and loose bite. You may have to play around to find the sweet spot between speed and driveability.

      David M
      Current Mqko - 1990 Mako 211 w/2006 250 E-TEC. http://www.classicmako.com/forum/topic.asp?TOPIC_ID=6226. [br]- Previous Makos 1987 20C, 1979 23\' IB, 1970s 17 Angler

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      • #4
        With the motor trimed down lay a straitedge alone the bottom of your hull and see where it comes in contact with your lower unit. The cavitation plate should be within 1/2 inch of that mark. Dont forget to reseal your mounting holes after your done. This formula has been discussed on many forums and I believe it to be true. It wouldnt hurt to run it past one of your mechanic friends though. dave
        [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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        • #5
          Any bright little techniques for twins on a bracket? When I'm flying through the air now in semi rough seas my motors don't cavitate. Is that a problem? [:x)] Isn't there a rule of thumb for bracket distance vs motor heigth?
          Artie Sutherland[br]Rude Attitude -\'76 Mako 25 CC. - SOLD[br]1976 Mako 21[br]2002 Yellowfin 31 - 300 hp Suzukis[br]Gulf Coast, Mississippi[br]

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          • #6
            Artie, I suspect your setup is fine, it is NOT desirabe to cavitate when coming out of the water a little. I did read someware that you can raise the motor X number of inches for every Y number of setback inchs.

            I think it was on this forum. Time to make the old search engine work a little. BY the way do you have 25 inch motors on your boat? dave
            [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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            • #7
              Artie, the general rule is that for every 12" of setback, the anti-vetilation plates should be 1" above the hull bottom.
              Brian[br]St. Leonard, MD

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              • #8
                This might help. http://www.stainlessmarine.com/insta...ketsingle.html
                Tony C.[br]S. Daytona, FL[br]Boatless...for now[br]

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                • #9
                  25" Dave. Looks ike they may need to come up a notch. oh boy !![]
                  Artie Sutherland[br]Rude Attitude -\'76 Mako 25 CC. - SOLD[br]1976 Mako 21[br]2002 Yellowfin 31 - 300 hp Suzukis[br]Gulf Coast, Mississippi[br]

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                  • #10
                    Took her out for a spin again yesterday. Man does that thing run nice; I can tell the motor doesn't notice the boat. It seems to be over-revving... 6500 seems high for WOT. Would a different prop bring the rpms down and/or give me more speed?
                    \'72 Mako 17, Suzuki 140 FOR SALE[br]\'74 Mako 19B Project FOR SALE[br]Seabird 21 Project FOR SALE[br]San Juan 28 sailboat [br]Wake, VA[br][IMG]

                    Comment


                    • #11
                      WOT should be around 5600 for that motor, I'm pretty sure. A bigger prop would do both, more speed and decrease your rpms. Call a prop shop and they'll do the calculation for you using engine hp, boat weight, engine rpms, and get you in the ballpark for the correct prop size.

                      I called H&H propellor for my application. They are in salem, Mass (978) 744-3806 great guys!
                      [br]Michael R. Delgado[br]1972 Mako 22[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=15745[br]1976 Mako 25[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=18013&SearchTerms=mako,25[br]

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                      • #12
                        Thanks for the ref, I'll call them tomorrow. Looks like I'll have to unload this shiny stainless prop! []
                        \'72 Mako 17, Suzuki 140 FOR SALE[br]\'74 Mako 19B Project FOR SALE[br]Seabird 21 Project FOR SALE[br]San Juan 28 sailboat [br]Wake, VA[br][IMG]

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                        • #13
                          Mub, you should be running about 19" on that motor. I run 20" with a heavy cup because I have a heavy 17 and a jack plate. I see your running your boat, do you still want me to send you that hydralic steering? Sorry about the delay but its been hell week here and I have the flu. Gary

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                          • #14
                            Andy, you can almost always use your shiney prop as trading stock towards the prop you need. you will pick up another 5 mph with the right prop.(my-guess) dave.
                            [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.

                            Comment


                            • #15
                              quote:


                              Originally posted by mrdelgado


                              I called H&H propellor for my application. They are in salem, Mass (978) 744-3806 great guys!



                              H&H Props, they are a good group of guys and are located 3 miles from my house. I spent lots of money over there when I was a kid that knew everything and was a little reckless in a 13' Whaler with a 50hp Johnson. If I remember correctly, I had 3 props, one on the motor, the other onboard for a spare and the third always seemed to be at H&H and I rotated stock quite a bit. I did lots of silly things that I hope my son never hears about, but that was many years ago. I'm starting to wonder how I'm hear to type this.....

                              H&H also has two other locations, Brunswick Maine and Essex Connecticut.

                              David M
                              Current Mqko - 1990 Mako 211 w/2006 250 E-TEC. http://www.classicmako.com/forum/topic.asp?TOPIC_ID=6226. [br]- Previous Makos 1987 20C, 1979 23\' IB, 1970s 17 Angler

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