...Need more info on the boat, that thing should be running at least ninety.
Bigger pitch, more speed, smaller pitch, better holeshot. Pitch is an imaginary thing. In theory, pitch is how many inches the boat moves in one revolution of the prop. In reality there are a shiton of variables. So in theory, if you have a 23 pitch prop, the boat will move 23 inches per revolution, or at 5000 rpm, 9583 feet ...make sense?...Reality then comes into play, weight of the load, coefficient drag, hull design, prop design...pulls those numbers way, way down. Blades are heavy, like un-sprung weight on a car (steel wheels vs aluminum), the most efficient blade is a single, but counter-weight might as well be another blade (two blade). Blades like clean water, the more blades, the less clean water at speed....and yes aluminum props are much faster. More blades, better holeshot (usually)...ski botes run six to jump the skier on plane quicker, more surface area, top end doesn't matter. Wheel (prop) diameter also plays a big part in that, fewer blades, bigger diameter, less weight, same surface area, higher RPM's...complicated. If you were running an outboard, I would tell you to add a jackplate and trim tabs, but since you are inboard ( or sterndrive) I would tell you to add trim tabs...or learn to use them if you already have them.
Trim tabs affect the lift of the stern as opposed to "trim and tilt" which affects the bow lift (there is a difference). LENCO elec tabs rock, no hydro lines to screw w/. And they're fast. Don't go out and put monster tabs on, because you will sink the boat and kill yourself. I'm assuming the boat is in the 20' class, I wouldn't go bigger than 9"x12" on it. What will happen is you will lift the stern of the hull off of the water creating less drag, then you trim the bow. If your RPM's are in a happy place right now w/ the prop you are running, then you will need to re-prop w/ a bigger pitch. Props are very complicated, the rake in a prop creates bow lift, and the pitch determines speed (more or less), if you "cup" a prop, it will hold more water, but you will lose top end from the drag. A REAL good prop guy is a blessing, find a prop you're somewhat happy w/, tell him what it's doing and not doing at different RPM's, and let him put the hammer to it. It'll make you happy.
My boat is a purpose built for fly fishing in very shallow water, it is a 17' carbon fiber hull, that weights 250# and is powered by a 60 horse, it tops out at 37 mph, but get's up in what it will float in ( about 7 inches loaded) and will do that in half a boat length because that's what I need it to do, and it will run in wet grass w/ the plate up. I built a prop "vise" and hammer my own props til it feels right. Hell, I knew guys that kept hammers and mapp gas on their boat and did it on the water!
I used to run an 18' bass boat w/ a 150 (back in the late 80's), I could leave most 20's w/ 200's standing still at 65 mph. w/ a top end of 78mph GPS'd...My prop guy listened to me and did what I wanted, and I had a jackplate...and it was a badass hull design.
A little speed tip: don't wax the bottom of the boat, scuff the "pad" (where the boat runs on plane) crossways to get more air under it, less friction (old racer tip). Hydrodynamics are a mind boggling thing...the electrolysis that happen when a prop is spinning in itself is just freaky. I know a guy running a 350 Merc OB that will top out at 98mph on a fishing boat...he says it does use more fuel, but since he get's there in half the time it balances out. (And I've seen him shear 1/2" stainless bolts on his jackplate)...the "Scalded Ape" is the name of the boat, and yes, it has the grafix to match the name. It's a 22' tunnel, it scares me just to look at it.
I'll do what I can to help, I'm not much on inboards, but I kinda know how most of it all works...
I hope that made sense, there's a lot to take in (kinda like woods buggies to me). Good Luck, Tx
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