RAJ Dyne w/3 Optimax 300xs Mercs

Discussion in 'Tom Miller Boats' started by rajboatdude, May 4, 2007.

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  1. jim

    jim Hydrodyne 18 Specialist

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    77 Dyne 18 I/O converted to Outboard
    Thanks for the information.

    I think you told me that you run your own gearcases. What ratio are you running?

    jim
     
    jim, Jul 9, 2007
    #11
  2. rajboatdude

    rajboatdude Established Hydrodyner

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    Jim,
    The newer ones are 1.75:1 but I think the older gearcases are rated at 1.78:1. When we ran the 2.5 L engines we changed gear ratio's to a high altitude kit which was 2:1's. Mercury 2.5's always seemed to like higher rpm's. The 3.0 L Opti's have a lot better torque curve.

    Edd
     
    rajboatdude, Jul 9, 2007
    #12
  3. jim

    jim Hydrodyne 18 Specialist

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    Did you mean to say 1.87?

    jim
     
    jim, Jul 9, 2007
    #13
  4. rajboatdude

    rajboatdude Established Hydrodyner

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    Opps, yea your right.
     
    rajboatdude, Jul 9, 2007
    #14
  5. jim

    jim Hydrodyne 18 Specialist

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    Thanks,

    That would be a potent combination.

    jim
     
    jim, Jul 9, 2007
    #15
  6. walk_on_water

    walk_on_water Established Hydrodyner

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    17.6ft dyna-ski 2006
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    club de skinautique
    hey i got a question.... wth two motors they are counter rotating...but with three what is going on ? is the middle one counter rotating?
     
    walk_on_water, Oct 27, 2007
    #16
  7. 2MERCS

    2MERCS Administrator

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    That is usually what happens. My parents had a 30' Hallet with triple 2.5 mercs. The outer motors ran normal with 24 pitch props, the center ran counter with a 26 pitch.

    Daniel
     
    2MERCS, Oct 27, 2007
    #17
  8. walk_on_water

    walk_on_water Established Hydrodyner

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    why was the middle motor given a different pitch ??? does it really matter ??
     
    walk_on_water, Oct 28, 2007
    #18
  9. 2MERCS

    2MERCS Administrator

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    It could have been the other way around on the pitch but I believe it had something to do with the steering of the boat or the cavitaion in turns, the center motor was set 6" lower then the outside motors due to the vee hull. It ran about 91mph topped out at 7500 rpm the thing had a burn rate of 40gph. The motors had racing lower units, the oil injection stripped off a slightly decked head to give it more compression and they were set back almost 2.5' from the transom. All in all the motors were cranking out around 290hp apiece. Very cool boat though I will have to find a picture and talk to my dad about why he had the props set that way.

    Daniel
     
    2MERCS, Oct 28, 2007
    #19
  10. rajboatdude

    rajboatdude Established Hydrodyner

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    walk_on_water

    We run the center and right motor standard rotation and the left counter with 15 pitch 3-blade Mirage-Plus's. We use 6" jackplates and the center motor is about 2" lower than the outside motors.
     
    rajboatdude, Oct 30, 2007
    #20
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