Here is a intresting issue
A friend of mine just repowered his kencraft he went from a 150 yam.hpdi to a 150 yam 4 stroke. The boat would run 43 with the aged hpdi now with his 2007 4 stroke he is only getting 37 that is 6 miles per hour. Both are turning max rpm. The 4 stroke burns alot less fuel than the 2 stroke did but it does not perform as well. The dealer tried moving the motor up some holes and down some holes no change, even different manufactures of props no change.
question 1:
Is it the horse power to weight ratio? The HPDI does not weigh as much as the 4 stroke.
question 2:
Is it the way the motor is rated Hp at the prop or at the power head?
question 3:
Are the new emission standards effecting performance?
question 4:
Or does it just come down to the old saying to generate horse power you have to burn fuel?
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