Fish-Hawk.Net

i have a etec 150hp with a viper 19 pitch 3 blade stainless steel prop,

if i change the prop for another model and keep the same pitch would it make a big difference on take off and top speed,
or i have to change the pitch too to see the biggest difference?

Give Canada Propeller a call at 613-249-0231. They've done me well in the past.

It'll make a difference if you went from a stainless to an aluminum prop if you kept the same pitch.

But for the most part, unless the new prop has more cup than the old and you stick with stainless, you would have to change the pitch to get different results.

If you want better whole shot, go down a size and if you want more top end, go up a size. But make sure you are in the Max RPM of your operating range. If the motor cannot turn the bigger prop to max RPM at WOT, you are putting more strain in the engine than is necessary.

Other options for good top end and better whole shot would be to prop the motor to max RPM and have some PVS vent holes drilled in by a good prop man so that air/exhaust can escape in front of the blade making it easier for the prop to turn when blasting off. Once you are at speed, the pressure from the water going over them doesn't allow anything to come out of the holes so it does not affect top end.

Adam

Hi, What boat do you have this on?
The boat type and what is equipped onboard will determine a lot of things.

I have the same engine as you on a 18.5' Phoenix Bassboat it originally came with a 24P 3 blade Raker2, with the help of the guys at Pirate Cove Marina we changed the prop to a 22P prop.
The added talons made my holeshot terrible but once we put the 22P prop the holeshot was much better.
The twin Talons not only add weight but they drag in the water during the holeshot and it drags in the wind while on plane.

With a bigger pitch you'll gain speed and lose holeshot, with less pitch you'll gain a better holeshot but lose speed.
But with that said you already have a 19P Stainless prop you must jump right out of the water!

I couldn't run a 19P I would be too close to the rev limiter when on plane and trimmed.

Shawn D

i understand pitch theory, but im wondering what is the difference between 2 model of prop?

lets take the viper and raker what is not the same?... lenght, blade pattern, size
its impossible that they are identical!

thats basicly my question

thanks

Lots of different factors involved, rake angle, thickness of blades,
cupping , type of metal alloy, etc., etc.
You have to research specs of each prop individually.
Mindboggling for the most part, you really have to try
props individually under varying circumstances and also
depending on what you intend to do with them.
You theoretically could/should have 3 or 4 props to
take on all different situations that arise.