The speed should stay the same.
Boats personallity in relation to different pitch will play into the sceme. Also true box stock props must be used.

The only reason to go to1.36 gears is if you run out of propeller pitch or in some applications run at or over the 34ish and up pitches.

Brett

off topic (sorry)

Brett
Bravo 4 blade
What would have to be done to this type of prop to give it less stern lift?

I had it worked and now I seem to be getting stern lift
(I didn't want to start a new thread for 1 question)

Ray

Call us and we discuss it in detail.

Who did the work? What was supposed to be achieved etc., etc.

B

Hey ray, I think you and I are having the same problem with the same LI prop guy
Email me [email protected]

Too much trailing edge cup.

I have been told that less pitch is more efficient than more pitch, especially at the upper ends of the scale. If you look at a tall prop, say 30" and up, look how close the blades are to being flat, as in paralell w/the water when the blade enters. Kind of slaps it. On the smaller boats I've run we always felt this caused a paddle wheel effect, trying to turn the boat instead of pushing it straight ahead like the more gradual angle of a lower pitched wheel.
On the race O/B's they gear the props way up and picth is cut approx, in half. Of course these are fly weight boats but theories are the similar.
I've done quite a bit of testing w/the smaller boats and here's couple of things I learned.

A. A boat wants what it wants regardless of what we think we know or what common wisdom says. I had a light fast (100 mph) O/B w/a motor that would make power and turn into the 8K range.
For going fast I assumed a gob of pitch and I'd be there. I ran props on that boat in 2" increments from 24" to 32" and saw 3 mph difference! I believe this had to do w/the torque curve of the motor and where it was happy. On top of that, the boat was the happiest w/a 26. Did everything well and was within 1 mph of the fastest which took all day to get there and had to be perfect conditions.

B. I built and rigged a similar motor for a customer and rigged it on his 21' Challenger. I put 1.62 gears in the Sportmaster to slow the crank down and speed the prop up. (in my mind)
My prop calculator showed 3" difference in picth (the motor felt) between that and the standard 1.87's.
Boat ran good but we ended up going back to the 1.87's to try and get the R's up higher where we wanted them. Basically changed that 3" of pitch w/the wheels, R's changed accordingly and everything else stayed the same.
Realistically, we saw no difference and this was back to back testing.

Brett, most of this is just my opinion and would be very interested in any input.

I was thinking about the "slapping" effect you talked about and thought the same thing until I thought about the fact that less pitch and more rpm just equates to smaller more frequent "slaps" and in the end probably adds up to about the same effect. There has to be a point that makes sense to add rpm and not pitch but I'm guess most props wont be made in that pitch. probably why most bravo props stop at 34 or so.

I'm not completely clear on the question.
If it is, Are lower pitches more efficient than higher pitches? I'd have to say yes,sometimes. You can say that as a general assumption for the reason you described. However, we have set up literally thousands of boats with 30 plus inches of pitch and are running in the 10% or less ranges. Look at the large Mystics and MTI's. We have those boats running 40-41 inches of pitch at 8-10% slip.
If you could have a propeller propelling on its own without a out-drive or boat, it would be 100% efficient whether it is 15 pitch or 40 pitch.

Paddle wheel effect is a reality and is more prevalent with certain propeller geometry's and and of course boat set ups.

Bravo 1's stop at 36. We make them up to 38.

Again, #1 is to operate the engine in its recommended range using gear ratio and pitch to control that final rpm. Ultimately going up in pitch and down in gear ratio(larger numbers) will reap the same speed at WOT with different throttle response times. This is why I tend to lean towards the lower gears and higher pitches up to the 33 ish range in Bravo drives . #6's are different.

Brett