Prop Pitch

[coachgilley]

Can someone please share some information with me about the difference in the pitch on propellers. I recently bought a newer bass boat that has a 3 blade, Mercury Tempest 25 degree pitch Prop. My boat is a 20 feet long with a 225 Optimax. I am familiar with the differences between 3 and 4 blade props but, what is the difference in performace say between a 21 degree pitch and a 25 degree pitch? Thanks!

[912nitro]

Call Phils Propellar & talk to the prop guy... he is a expert.

[SloppySeconds]

The pitch on a prop is the horizontal distance the prop will travel during one revolution - so your 25" pitch prop goes forward 25 inches in one turn. That means it has more grab to the water, but will be harder for a motor to turn at low RPM. A lower pitch prop will have less resistance against the water and will be easier to spin. These types of props are good at getting a boat moving to start, but don't have much "top end" when it comes to getting a boat to a high speed. This is why some heavy boats that want hole-shot go with lower-pitch props - such as ski boats and runabouts. The amount of pitch your prop should have should depend mostly on the size of the motor and the weight of the boat. Bass boats with 225's have a lot of power and lower weights compared to big ski boats with the same HP. This is why you often see them with larger-pitch props. There seems to be a sweet spot of hole-shot and top-end that can be hard to find, but not impossible. You may have to play with some different props and jack-plate heights, but I think the prop you have is probably pretty close already.

As many others have stated in the past, the rule of thumb for your prop should be that at wide-open throttle (WOT), your motor should be at or just below it's max rated RPM. If it is too high, increase the prop pitch, too low, decrease the pitch. One inch of pitch will usually result in 200rpm change.

If your boat is currently running fine with a 25 pitch prop, going to a 21 will be a bad idea. A 21 pitch prop would increase you motor RPM by about 800rpm - which I suspect will be way too high. Those 21 pitch props are usually found on smaller bass boats with 90-115 Hp motors.

Of course, the style of prop does matter a little, but this is secondary to the pitch. Some props have different blade styles, with more cupping or chopped tips etc... These will change how the prop performs, but the pitch is the most important.

[coachgilley]

Sloppy: Wow great information! Thank you. This is my first time posting to this forum, and I appreciate all you help.

[SloppySeconds]

I'm sure that you will find a wealth of information here. If you want a lot of other propeller tips etc... you might try looking into the "setups library" on this page to see what other folks are using for your boat/engine combination.

http://bassboatcentral.com/supertips.htm

You may also try posting your specific questions here:
http://bbcboards.zeroforum.com/zeroforum?id=11

There's lots of good folks out there that can at least offer some free advice... whether you get what you pay for is up to you!