Fresh Water Runabouts

[Sixxxxer]

What is pitch for a Prop...Like gearing for a car/bike?

[CasterTroy]

Originally Posted by Sixxxxer

What is pitch for a Prop...Like gearing for a car/bike?

Exactly. Hole shot vs top speed

[Sixxxxer]

Got ya.

Makes sense. Just never got into Boats much

[LeeNetworX]

Originally Posted by Sixxxxer

What is pitch for a Prop...Like gearing for a car/bike?

Pitch is how far it will travel forward in one complete rotation, in inches. So I went from 19" to 17", with the objective being to get more spin in a same linear distance, thus providing more thrust powering up from an idle, to ease in pulling a skier/wakeboarder up out of the water faster. Hope I'm explaining it correctly, this stuff is relatively new to me.

[OneSickPsycho]

Originally Posted by LeeNetworX

Pitch is how far it will travel forward in one complete rotation, in inches. So I went from 19" to 17", with the objective being to get more spin in a same linear distance, thus providing more thrust powering up from an idle, to ease in pulling a skier/wakeboarder up out of the water faster. Hope I'm explaining it correctly, this stuff is relatively new to me.

That's it as far as I know...

[fasternyou929]

Originally Posted by LeeNetworX

Pitch is how far it will travel forward in one complete rotation, in inches. So I went from 19" to 17", with the objective being to get more spin in a same linear distance, thus providing more thrust powering up from an idle, to ease in pulling a skier/wakeboarder up out of the water faster. Hope I'm explaining it correctly, this stuff is relatively new to me.

Don't know why but this thread randomly popped into my head today. I'm no boating expert (as I'm about to prove), but wouldn't 19" of forward motion per rotation give you a better wholeshot and pop a skier out of the water quicker? I am definitely missing something though, because by that definition a 19" would provide better accelleration AND higher top speed than a 17" rather than a trade-off.

I assume there are some fluid dynamics that come into play similar to HP and Torque, I'm just having trouble visualizing which pitch favors which.

['73 H1 Triple]

Originally Posted by fasternyou929

Don't know why but this thread randomly popped into my head today. I'm no boating expert (as I'm about to prove), but wouldn't 19" of forward motion per rotation give you a better wholeshot and pop a skier out of the water quicker? I am definitely missing something though, because by that definition a 19" would provide better accelleration AND higher top speed than a 17" rather than a trade-off.

I assume there are some fluid dynamics that come into play similar to HP and Torque, I'm just having trouble visualizing which pitch favors which.

A 19" pitch prop will have a slower holeshot versus a 17" pitch. Think of the 19" as highway gears and the 17" as drag gears.

On my 4.3L powered 18' Celebrity, I added a "whale tail" to the lower unit. At the expense of about 2 mph on top end, I get much better hole shots ( made a BIG difference pulling water skiers) and increased stabilty in rough water ( less rocking)

[goof2]

Originally Posted by fasternyou929

Don't know why but this thread randomly popped into my head today. I'm no boating expert (as I'm about to prove), but wouldn't 19" of forward motion per rotation give you a better wholeshot and pop a skier out of the water quicker? I am definitely missing something though, because by that definition a 19" would provide better accelleration AND higher top speed than a 17" rather than a trade-off.

I assume there are some fluid dynamics that come into play similar to HP and Torque, I'm just having trouble visualizing which pitch favors which.

If the engine wasn't fighting against friction and mass you would be right. With those in play the 19" is going to accelerate slower and take longer to get up on plane.

To compare it to something you are more familiar with look at motorcycles. Using the same logic 6th gear (19") would give better acceleration and top speed than 1st (17") since 6th gives more forward motion per rotation than 1st. For essentially the same reasons as a boat accelerating the mass of the bike and overcoming friction means this is not the case.

[Turbo Ghost]

Then of course, you have to walk the fine line between thrust and cavitation! Too shallow a pitch and the prop will rip through the water and not gain any forward traction for the force applied. It's like everything else, it's a trade-off between holeshot and top speed. As previously mentioned, whale-tails make a huge difference in holeshot at the expense of top-end. They also help make slightly smoother wake for wakeboarders and the like.

[Rangerscott]

Pitch doesnt matter much when youre hitting stumps and boulders. LOL. Are lakes are ponds now.