Re: go faster
At 30 your pretty much right on.A 25 Etec on a 280lb Alumacraft utility 2 men 6 gal gas, battery and gear 2.15 gear ratio 10.3 X 12 al prop tested at 31.6mph.
at 4500rpm 21.5 mph 16.9 mpg.
A few things to try::Start with a tach and a gps.
A tinytach is about $47 and easy to install.Do some test runs and give us the prop size,max rpm and speed.Max rated rpm is 5,600 and you should shoot for that area.
The antivent plate just above the prop should be visable on plane.
Raise the motor till it is or to a point just before venting(cavitation) becomes a problem.There are props that will allow maximum height.The al. Turning Point Rascal is one that is reasonable and effective.Unfortunately while these props have been very effective they are somewhat unpredictable.I do believe Turning Point will exchange props to help you get the right one.Of course there are ss props that do well but are expensive. Trim adjustment is important sometime one hole isn't enough but the next is too much;you can buy or make wedges to help fine tune the trim.
Generally a rearward weight balance is faster;the idea is to have as littlle boat in the water as possible.A Jon will get up on the water easily but usually has 3 keels and lots of rivots.Not the fastest bottom.Weight elimination and placement is important.A 3 gallon plastic gas tank is a thought.A 25 will run over an hour at wot
on 3 gallons.If you have electric start a Garden tractor battery will save weight and serve well as a starting battery on a 25.If you have a charging system you do usually need to have a battery in the circuit.