prop survey

[tnltracy]

I have a 13-3/4 x 15 aluminum currently. Last year I was getting around 24MPH at 5500 RPM by GPS. Start of the year I was showing around 29MPH, but her butt got a bit dirty over the summer

At WOT, the motor would over rev well over 6k RPM, so I've been shopping for a new prop this year. I just picked up a used 13-1/4 x 17 that I'm hoping will take RPM's down a tad and give me a few more MPH's. Will report once the boat gets into the water

[kman104501]

I have a 19 pitch ss, not sure what dia, 225 Evinrude, WOT 50MPH after being in the water for 1/2 a season. Always wondered if it would pay to go slightly larger....

[Genie Aye]

Originally Posted by kman104501

I have a 19 pitch ss, not sure what dia, 225 Evinrude, WOT 50MPH after being in the water for 1/2 a season. Always wondered if it would pay to go slightly larger....

At WOT with a average load--what rpm are you at?

Rpm will tell you if you are prop'd right or not--you do not want to over prop for sure.

[kman104501]

Originally Posted by Genie Aye

At WOT with a average load--what rpm are you at?

Rpm will tell you if you are prop'd right or not--you do not want to over prop for sure.

I am able to get to 5600RPM without a problem with 3 people, full tank of fuel and fishing gear (of course).

[Destroyer]

Originally Posted by tnltracy

I have a 13-3/4 x 15 aluminum currently. Last year I was getting around 24MPH at 5500 RPM by GPS. Start of the year I was showing around 29MPH, but her butt got a bit dirty over the summer

At WOT, the motor would over rev well over 6k RPM, so I've been shopping for a new prop this year. I just picked up a used 13-1/4 x 17 that I'm hoping will take RPM's down a tad and give me a few more MPH's. Will report once the boat gets into the water

Pitch is the theoretical distance that a propeller will move through the water in one revolution. (not counting slippage). So a 21p propeller will move 21" through the water in one revolution...a 15p will move 15" etc etc. As a general rule of thumb, expect to see a 300-400 RPM DECREASE for every 2 inches of pitch that you INCREASE your prop. (Propeller pitch is normally changed by a factor of 2"....13,15,17,19 etc.) Find out what the recommended WOT RPM's are from your motor's manual, and then size your prop until you arrive close to it. If you are into watersports like tubing or sking you'll want to go down one size in pitch, which will result in better pulling power and faster hole shots but less top end speed. If you're into going places in a hurry you'll want to go up one size in pitch which will result in a faster top end but less pulling power and longer time to get up on plane. In all cases stay in the recommended RPM range.. over-revving or lugging your motor will result in a greatly shortened motor life.