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  1. #1
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    Concord Mach 2 set up

    Anyone played around w a '86 Concord Mach 2 set up? Mine still has the stock 19" swim platform/setback bracket. Power is a 25" 2.5 200 Merc and a 23" through hub prop. Best speed has been 63 mph on gps @ 5800 rpm while porpoising almost uncontrollable at neutral trim. I will be doing a complete structural rebuild this winter and probably won't be putting the platform back on. I'm thinking a 14" hydraulic jack will be a good start.

    Thanks for any info

    Pat

  2. #2
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    Pat

    i have a 97 Mach II with the stock 18-19 inch set back with an additional 3inch manual jack plate. The boat is actually running a 20 inch 300 Merc. Performance is great with this setup. I recommend reinstalling the factory setback platform as it distributes the engine torque and load across the entire transom and a standard jack plate only distributes it across the engine mount surface.
    Love those concords!!

  3. #3
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    I am also getting 80 on the gps with a 24 fury. Mine does porpoise more with a three blade and is completely gone with a four blade. Also loses some speed with the 4 blade

  4. #4
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    Hey MercRoy, saw you at the beach yesterday and that is a super nice concord you have there.
    1971 Sidewinder 14 SS w Johnson 90 v-4
    1959 Texas Maid Falcon w Mercury Mark 35A
    1981 Sylvan Sportster w Johnson 85 v-4
    2006 Harris pontoon with a Yamaha 90
    1969 Sunfish sailboat

  5. #5
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    Hey turtleherder Thanks
    it’s coming along fairly well

  6. #6
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    Thanks for the reply MercRoy. I was thinking all that set back was a major contributor to the porpoising. What speed and trim position does the porpoising occur on your rig? I ran a 20" on mine for half this summer, propshaft height about 1 1/4 below the pad, and it worked fine at 45mph and below in calm water. In rough conditions, this set up had a tendency to nose dive, allowing the prop to lose bite. Plus the porpoising was so bad over 50 the best speed I got was about 57. When I switched back to a 25", prop shaft height is 4 1/8 below the pad rough water handling was great and the boat responded to trim input much better. Now I can go 53- 54 before the porpoising starts. Over 55 it goes ape **** til 62-63. I think after the restoration and some more set up time, its going to be a kick ass rig

  7. #7
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    From my experience your symptoms are pointing to proper engine height and prop selection
    20 in motor set 3/4 above pad with a 24 fury and full tank of fuel. I have some porpoise at approx 73-76 but nothing that is out of control or unsafe. With 1/8 tank the porpoise is gone all around and picks up 4-6 miles per hour. porpoise is extremely more noticeable with 25 tempest under exact same conditions and is 8-10mph slower. Porpoise is completely gone Utilizing four blade 28 or 24.

    my setup responded very positively with speed and porpoise when I went above pad but had to use prop like the fury or 4 blade to keep from loosing grip.

    What prop are you using?
    I recommend looking at prop selection

  8. #8
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    I think you're right on. It looks like blade area is the ticket for the Concord. The prop I was running is a Merc Laser 23 three blade. The only other prop I've tried is a Mere 21 thru hub cleaver, which resulted in the same performance.

    How's your set up work in rough water?

  9. #9
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    I see no change in performance in rough water
    big hub props is where it at with these machines!!

  10. #10
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    I do get prop slip on a hard hole shot just as the boat is planing out. I contribute that to engine height being too high. Hydro jack plate will fix that this winter

  11. #11
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    Hey guys, post some pics if you can. Thanks.
    You cannot bring about prosperity by discouraging thrift. You cannot strengthen the weak by weakening the strong. You cannot help the wage earner by pulling down the wage payer. You cannot further the brotherhood of man by encouraging class hatred. You cannot help the poor by destroying the rich. You cannot keep out of trouble by spending more than you earn.

  12. #12
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    Blade area, large hub, engine height and more set back. We’ll have to do some research on hydraulic jacks with minimal set back. I’ll probably be alright with and additional 4-5 inches of set back with my 400 lb 200. You might be at the limit with your big bad 300.

  13. #13
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    Well
    i agree but what’s another 2 inches gonna hurt

  14. #14
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    True enough. TH Marine makes a self contained 4” hydraulic plate. Bob Machine has a 4” as well, but a pump has to be mounted in the boat

  15. #15
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    I meant to ask what your favorite 4 blade is and how it effected performance and speed

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