Right prop for Yamaha 115

[CHANCE1234]

i'm currently running a 13 1/4 by 15 aluminum prop. i don't remember the brand. the engine is a 2001 yamaha 115 TXRZ (i believe) i'm not real mechanical so i don't know what the gear ratio is. i do have a line on a 17 pitch used alumium yamaha prop with a 13 1/4 diameter on ebay. i'm currently the high bidder, hopefully i can get it for cheap, as i'm the only bidder with a day left. i won't be in the water for about another month. when exactly do you determine your "on plane"? i have a video someplace of 13 my GPS at 13 knots which is what i determined to be on plane just be the feel and how the boat rode. but i'm not sure if there is a "book" answer for "on plane" i should not need a 4 blade as there is no weight back aft except for the engine, no livewell, etc... and there is no bow rise getting on plane.

[Bushwacker]

Originally Posted by CHANCE1234

. . . when exactly do you determine your "on plane"? . . .

I look at the wake . . . if water is coming cleanly off the bottom and flat for several feet behind the transom and water from around the sides is converging into sort of a rooster tail behind that, and you're at a point where you can rapidly pick up speed with additional power, I'd say you're on plane, even though the running angle continues to flatten out as you pick up speed. The Boating Magazine test on an I/O Seafari showed running angle continued to drop up to about 25 mph. It's optimum mpg was at 19 mph, where the running angle was relatively high, but it evidently didn't have as much hull in the water at that point!

[CHANCE1234]

Originally Posted by Bushwacker

I look at the wake . . . if water is coming cleanly off the bottom and flat for several feet behind the transom and water from around the sides is converging into sort of a rooster tail behind that, and you're at a point where you can rapidly pick up speed with additional power, I'd say you're on plane, even though the running angle continues to flatten out as you pick up speed. The Boating Magazine test on an I/O Seafari showed running angle continued to drop up to about 25 mph. It's optimum mpg was at 19 mph, where the running angle was relatively high, but it evidently didn't have as much hull in the water at that point!

good to know, thats how I measured it too. when i took my video it was with the previous engine a merc 115 before it blew up. i'll give it a shot in the pond hopefully late this month with both the 15 pitch and 17 pitch.