I personally run the 8 hp Mercury. I love it because the shifter is in the handle, and you don't have to reach to the side of the motor to shift. This would be plenty for your 17 foot boat. I run mine on a 18 footer, with plenty extra left over, and the 4 stroke would be the ultimate, but more money.
Keith
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It's time to put the red rubber nose away, clown seasons over.