You picked a really tricky subject to tackle.   I would advise you to stop there and ,first,travel to a show or large well attended club asap.   To stay true-to-scale and get a model to plane is harder the bigger you build.   Keeping water out an mtb,following magazine plans method was impossible.

I’ve done 3 MTB’s from 2 to just over 3 feet……Small one from plan was hard balsa with woven glass cloth+ epoxy. Larger ones were polester glass hull and a ply skinned hull .

 I found a 540 sized motor,uncooled, would get the 2 foot model on the plane no problem on calm water. It would easily fast electric boats  but ,scale rudder and single screw meant  it had huge turning circle in one direction. At that scale a 6V Ah lead acid battery was not too heavy and gave good duration.   It was before the era of metal hydride batteries.

I know how to get the right size of prop to get maximum power out a motor.   Even then you get 50% efficiency so I get a lot of heat build up after 3 minutes in both .

Going up to 3 feet increased the weight enourmously and I could only get scale mtb speed  .I’m guessing drag is also a factor as I’m not an expert in that field. Both the 3 foot (ish) models had twin 540 sized motors. I’m guessing a high power motor or upping voltage and watercooling motors would have improved speed.

In short………the bigger the patrol boat the more difficult to plane…..compromise on scale……fine tune prop size to get maximum motor power……don’t follow the plan if it means you cant mount motor/battery deep down in the hull……keep weight down.

If you stay small (2 feet) and light you’ll find things a lot easier