20 SF Prop numbers

[CHANCE1234]

1972 20 SF. 2001 yamaha 115 two stroke. Put in at local pond for shake down and anted to get some input on numbers I received via the Garmin GPS. All speeds are in knots. Prop tested is a yamaha aluminum 13 1/4 X 17 semi clever. I feel like im hitting the rev limiter at 5700 as I have throttle left and there is definetly a noise change when bouncing off 5700.

Trimmed all the way down:

3400 RPM 17.3 kts
4000 RPM 22.7
4500 RPM 26.2
5000 RPM 29.5
5700 (WOT) 33.4

Trimmed up:

3400 RPM 16.8
4000 RPM 22.2
4500 RPM 26.7
5000 RPM 29.9
5700 RPM 34.3

How do these numbers look? Surprised that speed did not increase by even 1 knot when trimmed up. Thoughts on other props? Thanks.

[FishStretcher]

Those numbers look decent to me. I get 28-29kts on a F100 on a 20MA with a heavier motor.

[billythekid]

I Would try to find a 3 blade 19 pitch.

[CHANCE1234]

I'm so confused about props. I have some telling me my results are good and others are saying I'm getting 25% slip which is pretty bad. Some are saying go down to a 14 pitch while others say go up to a 19 pitch. I think I'll have to call prop gods.

[flyingfrizzle]

Originally Posted by CHANCE1234

Some are saying go down to a 14 pitch while others say go up to a 19 pitch.

If you are hitting the rev limiter now with the 17 Pitch you defiantly don't want to go down in pitch to a 14p! You would be better to increase it slightly to a 18 maybe 19. If a 3 blade 17p is on the limiter try a 17p four blade, it will give you some rpms back and be more like a 19 3 blade. Ken at prop gods knows his stuff. Listen to him- He knows

[mnwnvc]

I am running a 13 1/8 X 19 SS Michigan on a 115 Opti and can top out at 41 mph. GPS. I am a little shy of max rpm but like the way boat runs. Do not have mid range numbers recorded will get those when ice breaks up.

[CHANCE1234]

So Ken at prop gods reccommended the Powertech SCD3 with 18 pitch. The other option would be the SCD4. I know the four blade is a stern lifting prop. I don't need to use tabs hardly at all but was wondering if the 4 blade would give me less slip and better economy. Anyone running somthing similar to these on a 115 yami?

[FishStretcher]

34.3 knots is 39.5 mph. That's not bad. I calculate more like 16% slip. There might be room for modest improvement? I have a Solas amita 4 blade 17"p you could try. It fits the F100- should fit the 115 yamaha. It is a tiny bit too much for the F100

[CHANCE1234]

Fish stretcher, where in Boston are you? I'll actually be in Boston tomorrow at the coast guard sector around 3:30 or 4.

[CHANCE1234]

Thanks frizz. I'm waiting to hear back from fishstretcher to borrow his 4 blade for a test. I hate spending money on props only to discover I need a different one and half to sell it for a big discount cause it's used.