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RePower J140 on 1973 Mako 17

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  • RePower J140 on 1973 Mako 17

    Irebuilt a 1973 Classic 17 last winter and now trying to make her GO.

    Have smooth running rebuilt 1994 J140 V4 but am having the following issues

    Easy start, smooth idle, responds nicely to throttle with no load

    When under load there is a slight vibration around 2,500rpm as the boat begins to plane, sounds like the engine is working too hard
    Around 3000 rpm the the vibrations and growl get worse
    Around 3,500 the boat comes onto plane and the symptoms subside
    WOT around 4,800 rpm and smooth running at 28kts

    It's running the prop that came with it, 13.25 - 13.5" diameter, don't know pitch

    Any suggestions would be much appreciated.
    Thanks for your consideration.