I don't believe it to be cupped. According to the size and specs of the current 12.75x17 prop I believe it to be a Solas 4 blade prop. That's why I was looking at the hustler 4 blade prop in the 13x17 prop. It runs great at that range but would like just a little more if I could get to 35 mph I would be happy. I like the way it performs now but I feel it can do a little better.
In your opinion with the info that I gave you what pitch would be the best to get my toms up but still maintain good hole shot and top end?
My opinion: Something has to change. If you weren't loading up your engine with what you have, your rpms would be higher. I keep mentioning blood out of a turnip, but that is what it is. You need more ponies, less slip maybe, or less drag.
Upping the ponies.....obvious
Less slip.....prop with more grab to propel you faster considering nothing else changes which it will. 2 things will change: either the increase in grab will not change the "aquadynamics" of your boat and the drag will remain constant causing the increased load to pull your rpms down farther than they already are and then it's a trade off between engine capabilities vs less prop slip. One thing you never see is the torque curve. Funny as it may seem, back in '68 when OMC came out with the "Triumph" (the name given to the 55 hp, triple, loop charged, Evinrude half of OMC's 2 stroke technology triumph) I was in a dealer one day and posted on the wall were several advertising banners illustrating the merits of the engine in an effort to boost sales. Posted clearly on one of those banners was the torque curve of the engine. Obviously I have forgotten what it looks like. We are still working on the "engine loading potential" of changing the prop's grab so don't get lost.
HP =[Torque (ft-lbs) x RPM]/ 5252 which is the standard, industry published, "quickie calculation" for HP. If the torque curve peak is back around 2500 rpms, and falls off as rpms increase (which is the norm for most internal combustion engines) as you load up the engine and pull the rpms down, the torque increases, meaning that your available HP may remain constant. So now this different prop with more bite is not loading the engine as much as it might have and the result can be an increase in MPH.
Less drag: How much drag is on your engine when you rev it in neutral? Not much. How fast and far do the rpms ramp up? Fast and far..........
Getting the hull out of the water reduces drag. On bass boats there is usually a dead rise (v shape) until you get to the bottom center of the hull and then the v flattens out to a horizontal line. Line is roughly 10" wide. Length may be half a dozen feet or so, but at WOT not much of that is in use. This is referred to as the "Pad" and BBs ride the pad when they want to be the first to their favorite "honey hole". The area of the hull touching the water is less than 60 square inches when hooked up on the pad with the trim set correctly and all that. The boat may weigh 3000# and be 20+ ft. long but the water interface doesn't know that. Result lightening fast speed for what a given hp engine could produce otherwise. Had the boat not been on the pad, the exposed area would be 50 times that and no way could you get any kind of dazzling speed out of that.
As your boat increases in speed after planing out, you are reducing the drag due to less hull to water contact. Anything you can do to get the spray finer (smaller droplets, aka misting which happens to a greater degree as speed increases) and break away from the boat farther back toward the transom is lightening the drag and it is an accumulative effect; the faster you go the less drag, the higher the rpms the higher the thrust which pushes the boat faster, etc. etc.
So change something and you can get more from what you have.
Might try this. Get some help first, another person. With your boat on your trailer parked on a concrete surface, carefully unbolt it from the transom while holding it where it can't fall over. Using your tongue jack on your trailer, jack the front (bow) of the boat up which will cause the transom to go down. Continue until you can put your mounting bolts in the next hole down on the engine. This should put your transom clamp bracket, that used to be sitting on your transom, 3/4" above it. Bolt and seal everything back down like it was and take it out and run it, recording data.
Come back with the answer with respect to hole shot performance, tight turns at high trim angles an high throttle settings, heading into reasonably sized waves at a fairly high speed and high trim angles, and just straight flat out running. Engine trim is important in this test so trim for the best performance so that you have a feel for what has changed.
Two things will come into play: Your boat should feel a lot lighter to the helm (steering) and with your trim set to the best position you will probably gain a couple of mph or more if the aquadynamics of the boat get into the picture like they should. What this may cost you is a little ventilation you don't currently have....ventilation defined as the engine revving up under turns or rough water and speed falling off slightly. If you get there, you just solved your problem with engine loading and buying a cupped prop will either solve or minimize the ventilation with the right trim position which is usually tucked in a little from where it was when you were running at WOT in a straightaway. So you may be able to get your desired "little bit more" with nothing more than a prop change. But I'll tell you right now: What you get out of this effort of your's won't be enough, regardless of the number. It's called human nature. Wink!
I'll wait for you.
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