Re-powering my 17.6

Discussion in 'Engine Questions' started by Dyna-Kid, Oct 9, 2012.

  1. Dyna-Kid

    Dyna-Kid Boat of the Month

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    Guys,

    I'm looking for some input on replacing my 150hp Optimax and re-powering my 17.6.

    My first choice would be to go with a brand new 150hp Opti, but I've heard a lot of good things about Mercury's new 150hp 3.0L 4 cyl fourstroke. Both the weight and price increase of Mercury's new 4 stroke is marginal, and fuel economy is not that big of an issue. I like the idea of having a quieter, smoother running engine behind me, but will a fourstroke have enough low end torque to do the job?

    Has anyone out there driven this new motor yet?

    Thanks in advance.

    Kevin
     
  2. Must-Ski Motors

    Must-Ski Motors Hydrodyne 20 Specialist

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    Waterhawks Ski team in Waterloo, Iowa ran a pair on a twin rig this year. They have 2 for sale. I am not aware of any other teams who had them. They might be your best bet for first hand info on how they compare in power vs the 150 Opti.

    They have an ad on showskiers.com.
     
  3. Must-Ski Motors

    Must-Ski Motors Hydrodyne 20 Specialist

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    One thing I would suggest as you are checking out that four stroke:

    In 2004 we built a triple 150 Yamaha inline 4 cyl 4 stroke boat. One thing I learned is that weight is one thing, but where the engine carries that weight can be equally important. Compared to the Evinrude 2 stroke V6s, the 4 strokes carried much more of their weight further back away from the transom and that created more bow rise and the boat sitting lower in the back.

    One of the reasons that the 2 stroke 150/175 Evinrude 60 degree V6s is such a great ski boat power plant is because of its center of gravity.

    a 150 might be the same HP at the prop, but it may affect the balance of the boat due to its construction.
     
  4. Dyna-Kid

    Dyna-Kid Boat of the Month

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    Club de Skinautique
    Thanks Erich.

    I hadn't considered the CG for the new four stroke and just by looking at the new motor it appears that the block sits further aft than it does on an Optimax?

    The dry weight of the new 150 four stroke is only 455 lbs as compared to 431 lbs for the 150 Opti's, but I will also have to consider the mounting angle to the transom in regards to nose down trim limits. Right now I'm using a transom wedge to get the required nose trim needed with an Optimax and will most likely have the new four stroke mounted with the same wedge?

    Kevin
     
  5. Must-Ski Motors

    Must-Ski Motors Hydrodyne 20 Specialist

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    yeah add 5-6 quarts of oil to that, not that that is huge but still something.

    It may affect the boat a bit, probably not too much. Would be interesting to see how the low end punch is on it vs the 2 stroke. The gearing is 1.92:1 vs 1.86:1 and throttle range is 5000-5800.
     
  6. Dyna-Kid

    Dyna-Kid Boat of the Month

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    Ski Team:
    Club de Skinautique
    The oil tank for the old Optimax will come out, so there's a small reduction in aft weight right there. But as you pointed out, oil would be addded to the top end of the four stroke.

    As to be expected, the new Merc 150hp four stroke revs up slower than the 2 stroke 150hp optimax, but it appears that the power/torque at the lower end is there. Some are saying that Merc's new four stroke 150hp is under-rated and is really putting out about 165hp at the prop and can be tuned to 200hp?? 17.6 Dynes and Dyna-Skis are Coast Guard rated at 150hp so the new Merc 150hp four stroke may be a good fit.

    Will probably try my current Alpha 4 Merc four bladed 16"P prop first and work from there. Might even go to a lower pitch if necessary.

    Darn it!! If only Jim had bought this motor first I could've gottin an comprehensive report!! :D

    Kevin
     
  7. dynebob1

    dynebob1 Boat of the Month

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    Kevin,

    What's wrong with your old Opti ? Just worn out ?


    Bob
     
  8. Dyna-Kid

    Dyna-Kid Boat of the Month

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    Ski Team:
    Club de Skinautique
    Hi Bob,

    Long story short:

    My '05 Opti was damaged in a freak storm that swamped my Dyna-Ski last summer. Of course you can't kill an Optimax or a Dyne and the motor still runs, but it really hasn't been the same ever since.

    I'm thinking of putting my '05 150 Optimax on my '74 Dyne and re-powering my 17.6 Dyna-Ski? I'm not sure if this is the right decision or not, and that's why I'm seeking input from you guys. Is Merc's new four stroke the way to go or not??

    Kevin
     
  9. jim

    jim Hydrodyne 18 Specialist

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    Thanks Kevin,

    When Mark Twain was traveling around the world, he held a press conference and was asked to comment on the reports of his death.

    HE SAID "THE REPORTS OF MY DEATH HAVE BEEN GREATLY EXAGGERATED"

    You people tend to have more confidence in me than I deserve.

    jim
     
  10. Dyna-Kid

    Dyna-Kid Boat of the Month

    Joined:
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    Location:
    Lake Metigoshe, ND
    Boat Model and Year:
    74 18 Hydrodyne 150 / 06 17.6 Dyna-Ski 150 Merc FS
    Ski Team:
    Club de Skinautique
    :lol: :lol:

    Jim,

    Not blowing sunshine up your arse, so please,,, don't flater yourself!! :lol:

    But seriously,, what are your thoughts about rigging a 17.6 with a four stroke...

    Kevin
     

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