My boat weights in at around 3500 lbs and I have a 8hp top speed about 6mph. I would recommend one of the High Thrust kickers with electric start , remote controls and tilt. ( i fish solo a lot and it's nice to control the motor from the helm, especially in rough weather) They have a bigger prop for more bite and a lower gear ratio in the lower unit so run at a higher rpm which is better for charging .
I am also a big fan of the solid mount brackets , the 4 strokes are heavier then the 2 strokes and need a pretty hefty bracket. If you mount the motor on a bracket that doesn't move you can connect it to the main with a steering link and never have to mess around connecting or disconnecting the steering.( the steering links never seem to float)
I added a nipple to my water separator filter and added the fuel line from the kicker to my main tank .
Good Luck !