Can one of you prop experts give me the 10 cent story on how different diameters of props work. For instance, what would the results/differences be on the same boat with a 16.5 X 33 and a 17.5 X 33 props on a #6 drive?...or a 16.5 X 29 vs. a 17.5 X 29.

Is it planning ability? attitude? speed?

I'm just wondering...and obviously bored out of my skull at work!!

get back to work...

Got off of work at 2:30

Thanks for your riveting input Sean!!

Wow that's a loaded question.

Larger Diameter propellers in general will produce more stern lift and of like pitch will bring the RPM down of course. And beyond that I need to know what hull and power package to speak on this topic.

Julie

Fair enough, I'll call you tomorrow.

No Don't call do here on this thread...this is a great topic.

Let's say the boat is a 35 fountain executioner....

With #6's???

I asked the question because I am re-powering my Top Gun with a pair of lower HP engines. It was running 16.5 X 33 four blades @6000rpm's. I've got a pair of 16.5 X 29's to try when I get the boat back. I no idea if they'll be right or not...but I'll be finding out in a few weeks

[QUOTE=OldSchool]With #6's???

I asked the question because I am re-powering my Top Gun with a pair of lower HP engines. It was running 16.5 X 33 four blades @6000rpm's. I've got a pair of 16.5 X 29's to try when I get the boat back. I no idea if they'll be right or not...but I'll be finding out in a few weeks [/QUOTE

If the boat handles well don't change the diameter. I ve had
three sets of the same props and they all responded differently.Seems like when I increased diameter 1" equaled
about 2" of pitch pitch. That was with 1:1 gears and 16.5X31s
Just my 2

[QUOTE=HotPursuit]Craig
I can tell you what my experience was with our Outerlimits. Our slip numbers were terrible at WOT. It was about 16-20%. We were running 16x34 4 blade Mercury cleavers. In an attempt to reduce slip we went with 17x33 4 blades. The slip went down the MPH went up. The down side was that it gave us much more lift on the stern, and magnified the chine walk that was already their. Very bad. The 34's were probably worked a couple of times and I should have had them checked out before buying new ones. I think you mentioned your boat was rock solid at speed. Thats something you dont want to sacrifice.

The key is to get the drive height, prop diameter, # of blades, and prop pitch just right. Changing any one of these variables will change many aspects of the boat's characteristics.

The best way to do this is by trying different props, then put in a spacer depending on the results with the first series of tests, then test again. It's very time consuming and few manufacturers spend the time, have the props to do this, or the knowledge. When you get into a high performance boat with a unique engine or drive package it may take a loot of time to get the boat dialed in just right.

Matt