I have an '07 Gordon Waterman 18 with a 2 stroke 70 Yamaha and I'm currently running a PowerTech RED3R14PYM90. I also have this prop in a 13P. I've run both but get a little better top speed with the 14. Hole shot is great with both. Jeff at PowerTech confirmed these were the best props for my set up. Having said that, I do not have a JP, so I'm not sure if my response is of any help.
I'm now running a Powertech SCD4 17 pitch. So far the best I've seen is 38.1 at 5800rpm's, but that was with 3 people with a full load and a 21 gals of fuel. What kind of numbers are you getting?
You're getting better top speed than me. The best I've seen with the 14P is 35 mph @ about 5700 rpm and that's with a light load. How's your hole shot with that 17?
It's very good, the prop comes alive once I have the jackplate at 3"-4". I'm considering getting a SCD3 18-19 and see how shes performs.
You're either trimming up to aerate that prop or cavitating badly because you're slipping 8 mph from theoretical speed of 46.1. You may find you will get better hole shot and overall fuel economy with a lower pitch prop that isn't slipping.
Jacked up to 4" and half trimmed. The prop is vented (so that helps on hole shot) and does not cavitate at all. Theoretical speed at 5% slip (which is where I'm at) is 40mph.
