Oh and here is an interesting post from one of the Skiers Choice Product Development Engineers regarding the move to 1.76 trans standard and why others use a lower gear by comparison.
Originally Posted by
goose 
Yeah, what he said. I am not sure exactly what type of "technical data" you want because I can spit a bunch of numbers out and truth is you can't probably prove them right or wrong. But what I can tell you is we spent a LOT of time driving the boats and you need to do the same. The theory behind the transmission is we were wanting to spin a bigger prop. Back in the day when boats were not as heavy and the engines did not have as much power, there was no need to spin a larger diameter prop. The boat didn't need it and the engine couldn't handle it. But now with the boats we have, the engine CAN handle it AND the boats need it. If you notice, that has definitely been the trend and we were not the only people to play with transmission ratios. The problem is everything is a tradeoff in propulsion. What we have found is the 1.76 is the best tradeoff we can see right now. With a 2.0 or larger ratio, you can run a larger prop. BUT, to get clearance under the boat you have to change the strut angle or something different. When you do that, you lose efficiency. Also, going to that requires a larger shaft, different shaft materials and other changes. If not done correctly, all that can be bad. Not trying to start any fights, but some people have had issues with that. By using the 1.76 ratio, we can turn a 15.5-16 inch prop using the same strut angles and still have proper clearance. AND with some testing, we now have 3 pitch options to go with the larger prop. For max low end, we offer the 15.5x15. For general purpose we offer the 15.5x16.5. For higher top end and lower rpm, we offer the 15.5x18.
Personally I ran the 15.5x18 all year this year. I love it! On the R&D Kaiyen I can get the boat about 43 mph unloaded and when loaded down for surfing it gets on plane good but really runs lower RPM's. The general idea is as you go down in pitch, you can get more weight on plane at wakeboarding speeds. Between the 15.5x18 and the 15.5x15, you can probably get about 1500lbs on plane with similar performance. If you are wakeboarding with 5000lbs or more and you do that often then maybe the 15.5x15 is the better prop for you. However, as you go up in pitch you gain speed AND lower rpms. You gain about 2 mph per pitch change. So, on a boat where you might get 42 or 43, the 16.5 is probably going to be about 40 and the 15 will be about 38. Also, as you go up in pitch, you lower rpms. Again, these numbers are rough, but I tell people about 200-300 rpm. So, if you are surfing at 3800 rpm with the 16.5, you would probably be closer to 3500-3600 with the 18. Again, everyone uses their boats differently, but some people on this forum have tried some of these props and you can probably get them to chine in with their personal examples also. For the way we use the boat, we surf a LOT, wakeboard with a lot of weight ONLY occasionally, and we sometimes go by water to a marina or different areas of the lake. By lowering the rpm at surfing, it is not only more efficient, but it lowers the noise. And then when it is time to get home or outrun a storm, the higher top speed is really nice. I have tried all the props and they all serve a purpose, just depends on what you want to be most important.
To sum it up again, the 400 with the 1.76 is probably similar to the 450 was with the 1.5, if not better. And with the new prop options, I think it is even more drastic. We offered the 450 with 1.76 last year and if you drove a boat with 450 vs 400 there was a HUGE difference. Now, with the 1.76 and prop options, you can get closer with just the 400. Because of that, I would imagine that most boats NOT at altitude can do fine with just the 400 with 1.76 and the right prop. If you are altitude, then you still might consider the 450 because it does have more power.
. Tall older guy is my awesome salesman who i had been dealing with for over a year prior and the younger guy is Drew Tinker of Skiers Choice. He's the son of Rick Tinker, owner of Skiers Choice. Really laid back guy and super nice. He handles a lot of the tours that come through the Kant as well and is very knowledgable of the process. What's cool is that these people welcome you like family. To this day I'm able to reach out to Drew just to shoot the crap or ask for something specific and he'll respond! My dealer has been equally as awesome and night/day from my previous dealer.
