As others have said we need several important pieces of information.

Tach/RPM at WOT

Drive ratio

Prop diameter, pitch and number of blades

Unless your boat is grossly over propped or mis-trimmed it is unlikely you will see a 5 mph improvement with a prop change and/or thru hull exhaust.

I can tell you that thru hull exhaust will net you zero performance increase (that is readily and consistently measurable) for your setup. If you like the sound thats one thing, but don't expect any significant improvement in performance.

Easy.. Motor has 350 hrs on it in an underpowered boat. Prob has a lot of wide open throttle time and is whooped. Pull motor, put in a 383 stroker kit and put on a 23 pitch prop. 50 mph boat.

Chris

Haha if I could I would... Maybe in the future but right now I can't afford to drop thousands on a motor lol

The below will take you down the quickest path and least money spent..

1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

That would be over-propped with that boat size and motor.

I dont think so.. 23 pitch 3 blade with a 383 and 24 ft boat would be perfect but that is not the direction he is going anyway.

Chris

With a 1.5 ratio that combo would be lucky to spin 4600 rpm. Likely lower.

I had a 24x7 heavy hull with a 330 7.4 mpi that turned a 21p right 4800. It would have been faster and turned a 23p if had a 383 400hp. It would be like throwing your girlfriends fat friend out of the boat and adding 70 hp. I know it would have turned 23

Chris

Ok finally have some numbers I'm running only 3800 WOT on smooth water with only me and a little over half a tank of fule with the motor trimmed up I currently am running a 19 pitch mercury marine vengeance

I would check the timing on the motor first then get a different prop. Just by a cheap aluminum until you figure which one you need. If timing is 10 degrees then try a 15 pitch from here

http://www.pbsboatstore.com/quicksil...9GkaApE28P8HAQ

It says these props are only good for 50 mph but I doubt you will be that fast any way. And your only out less than 100.00 the 17 pitch might also be an option. I actually might have one you can try for just shipping and would sell you for 50.00 if you are interested. Let me know and I will dig through my props.

Chris