Thread: A given for some
01-07-2007, 01:05 AM #1
- Join Date
- Jul 2006
A given for some
but others might not know this so I will post.
Prop Repitching and Blueprinting:
Thinking of getting a new prop? Before you do, consider the benefits of repitching your exsisting prop. If you already have a good condition stock or aftermarket stainless prop, you may be able to gain performance and save money by repitching your existing prop. Even new props will benefit from blueprinting the blades and repitching. One reason you would want to repitch a prop is to match it to the machine's powerband. Most newer props are progressively pitched meaning that they have a smaller pitch at the prop's leading edge that transitions to a higher pitch at the prop's trailing edge. Example- a prop designated 15/18 is 15 degrees at leading edge that transitions to 18 degrees at trailing edge. By repitching, the leading and trailing edge pitches of stock or aftermarket props can be optimized for your particular engine and hull combination. Even if the pitch of your prop is ideal, you could benefit from blueprinting. Most props have three or four blades. Unfortunately, the blades aren't all exactly alike, even on a new aftermarket prop. A 15/18 pitch prop might have one 14.5/18 blade, one 14/17 blade, and one 15/18.5 blade. Blueprinting the prop would ensure that all blades have equal pitches.
The trailing edge pitch is adjusted for top end performance based on peak engine RPMs at full throttle under load (pump in water). The optimum trailing edge pitch will limit your machines peak RPMs (not to be confused with a rev limiter - see below) to where your engine makes its peak horsepower. For example, if your engine makes its peak horsepower at 7000 RPM and your machine is showing peak RPM readings of 7200 RPM, you would want to raise the trailing edge pitch on that prop in order to bring RPMs down to 7000. A higher pitch decreases RPMs (takes a bigger bite of water) and a lower pitch raises RPMs (less bite). NOTE: A rev limiter electronically limits an engines RPM to a pre determined point. The rev limiter protects your engine in free rev conditions when the pump comes out of the water (choppy water or wave jumping). Typically the rev limiter is set to 500 or more RPM greater than the engine is capable turning while at full throttle under load (pump in water).
The leading edge pitch is adjusted for low end performance. The optimum leading edge pitch will allow the PWC to accelerate hard and let engine rev up quickly to high RPMs where more horsepower is made. A leading edge that is pitched too high (takes a bigger bite of water) will not let the engine rev up quickly to higher RPMs and acceleration will be sluggish or laboring. A leading edge that is pitched too low (takes a smaller bite of water) will rev up quickly but the prop will spin (or cavitate) causing slow acceleration. The judgment for repitching the leading edge should be made by the PWC's primary rider since the person's riding style and weight can effect acceleration.
This isnt my write up, I just found it and thought others might like to see.
01-07-2007, 10:07 AM #2
This is true. So where is the peak power band for the yamaha gpr 1300's?
01-07-2007, 11:19 AM #3
- Join Date
- Jul 2006
Thats a good question. I havent seen any dyno #s for these engines, especialy after mods where peak HP can change. I know people shoot for 7150 rpms so Im sure that would be close.
01-07-2007, 12:47 PM #4
7100-7250, single pipe..... (others will argue over this because they may not be in this range, so therefore the information must not be correct ) but here it is.
01-07-2007, 02:42 PM #5
yep...im at 7120 , so that info must be correct
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