Want to say Ive read here that the dead-rise and hull shape limit top speed to under 40 mph. A bigger motor is just going to get you out of the hole and on plane faster but offer minimal top speed gains. Ive been looking at new motors a bunch too and except the 70hp yamaha, everything else above 60hp will weigh 350+ lbs. Adding extra weight may not be worth it. 3 adults and a kid, 6-800lbs of gear, and a lot of fuel - you are probably over the boats weight limit which is what kills the hole shot and makes it slow to plane.
At altitude, my old 75hp would barely hit 30mph on a good day. Different props definitely helped the hole shot though, either the 3 blade hustler or 4 blade, without losing any top speed.
Last thing to consider is new motors are rated differently and are stronger for the equivalent hp rating. An old 70 is like a new 60. As much as I would love a 90 on mine, its rated for an old 85, and insurance wont cover me if I go above that anyway. Makes that 250lb 70hp 4-stroke yahama look very appealing. Been watching
@renns thread with his 60hp yama and makes me want one even more!!
