I agree with bushbear and tjn. Try to get an 18 footer. It won't be that much heavier, and you'll enjoy the extra room and sea worthiness. The longer length and extra width (?) won't require more horsepower under most considerations.

I would, however, stay with the 4 cycle engine. Just my opinion, but I love the quiet sound and the fuel economy. In Alaska for 8 summers I ran an 18 foot Klamath center console with a Honda 50 on it. It was a phenomenal fishing boat for two people - fished all day on 3 to 4 gallons of fuel. A little crowded with three. However, for fishing all the seasons around here, you will be happier with a boat with a windshield.