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  1. #1
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    exhaust mod omc 55 hp 2 cyl questions

    Engine is 55672e = 1976 55hp 2 cyl short shaft. I want to mod this engine for top end speed on a dux super light tunnel hull. No heavy loads,skiing, just going fast.
    Questions,exhaust mods? cutting out the rectangular restriction located between the mid and gear case, where the 2 bolt up. There is a rectangular rubber gasket that seals when bolt up. There seems to be lots of metal I could remove to open up this passage, at least 3/4 inch on sides and 1/2 both ends. Is this ok? or is this part of the tuner can?
    Question on compression , 180 lbs on both, tested several times 2 gauges, engine throttle open full and was cold. Is that about the max for pump gas?
    Question ignition? has terminal box cdi type, is there a rpm limiter? what is max rpm limiter setting? How to remove rpm limiter? ignition timing Idle? max?
    Question Carbs, what jet size
    Mods for 2 cyl omc? grinding,cutting ports? intake or exhaust?
    Thanks for help.
    Side note? I have this 55 rude 2 cyl and a 3 cyl yammy both 2stroke & shorts. Best or your choice what one to run on my super light tunnel? and what one responds to mods?

  2. #2
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    I am not very knowledgeable about racing motors but I would think that 180 psi compression would require some jet fuel mixture. I would think that jet size would be some trial runs and spark plug reading, I would start out a little rich.

  3. #3
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    Go with the yamaha, the 55 will have ignition issues. Plus the 55 must be carbon up pretty much to have that kind of compression.





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