Propeller difference

[PatRPS13]

Good day everyone!
I have a question for you guys, I just removed my propeller from my 1996 GSX to polish it. My friend who is giving me a hand have a spare propeller similiar as mine, the only difference is the end on mine have a straight cut and his have a round shape. Wich one will be better?

Thank you!

 

[red2blue]

I'd be willing to bet the shape of the trailing edge isn't the only difference.

Sit them both on a bench...top up. With a millimeter graduated rule...measure from the surface of the bench to the outside corner of both trailing and leading edges...of both props.

What do you find?

 

[Sportster-2001-951C-Stock]

The blade pitch is important, it's carefully matched to the power capability of your engine. Some aftermarket and perhaps factory impellers have a slightly different blade shape as you describe with the curved leading edges, yet may or may not be correctly pitched for the application.

So, there should be a number on the hub of the impeller you can search on to determine the manufacturers name and intended application. I would confirm it's correct match for your ski before installing it, if the pitch is too steep it may not perform well by causing the engine to labor and not rev properly, this could tend to cause your engine to run hotter than normal, top speed would likely suffer. Inversely, if the pitch is too small and unmatched to the torque curve of your engine, your engine might rev too much and overspeed or bounce off the rev limiter, top speed would also suffer in this case.

BTW, my understanding is surface finish polishing doesn't have any material improvement on performance.

 

[Coastiejoe]

Normally, a rounded impeller is an OEM (Factory) and an impeller with straight ends is an aftermarket.

 

[Seadoobuddy]

Is one better than the other?

 

[Sportster-2001-951C-Stock]

IMO, the very best prop you can get places the WOT engine RPM within the specified design limits. Anything else is subjective.

 

[Coastiejoe]

Is one better than the other?

Is one better than the other?

Well,, yes, maybe, no,, LOL

It is impossible to simply say yes or no. Reason being, if the aftermarket is of a different pitch compared to the OEM, then you will gain performance either in the low end or in the high end performance, And usually, if you gain it on the top end, you lose it on the bottom end.

However, Skat makes some impellers that are generally an over-all improvement by s small amount on each end and a better mid-range performance.

But as I type this, it occurs to me that you were asking if the rounded vs the straight is better/worse compared to the other.

Straight cut props/impellers are specifically designed to allow less drag and allow for higher RPMs. Round bladed spin slower but give a good general use across the entire speed curve.

 

[Seadoobuddy]

thanks, your last paragraph answered my question.

 

[PatRPS13]

Wow thanks a lot guys! That was really helpful! :thumbsup:

 

[Coastiejoe]

It HIT me as I was typing what you were really asking..

But,,, I had typed to much to delete things... LOL

 

[red2blue]

First think of a propeller as a gear, whether it be on a car or even a bicycle. The lower the gear, faster hole shot, more power, but revolutions are much faster so at a point you can only turn that gear so fast until you over rev the engine (or you legs). Now think of your car stuck in only 5th or 6th gear, very slow out of the hole, little torque, but eventually it will catch up with itself so you can cruise to a good speed.
The same basic concept applies to propellers, except with a prop you are committed to only one "gear". So what to do now? Find the prop size that will give the best overall performance. Sound difficult? It's really not.

Gonna disagree here....

Taller the prop...steeper the pitch..the better holeshot you will have because it's pushin more water. Because the motor doesn't have enough ass to get that prop spinning to max rpm...your top speed suffers.

It's why cc racers don't care about top speed as much as hole shot. They ain't in the throttle long enough to care.

You are implying that a prop you can cavitate outa the hole with...ie max out rpm, will eventually catch up and cruise at max speed. All things bein equal...prop ring gap ect....if you got the hp to spin a smaller prop at slow speeds...you'll leave speed unused at the top....ecu will make sure of it.