Prop Cup

Can someone explain the dis/advantages of prop cup? I'm looking at an OJ # 466 (14.25x14 1 1/8 .090 cup) vs. an OJ #475 (14.25x14.5 1 1/8 .120 cup). I realize the #466 will pull a bit harder out of the hole due to the "14" but what effect does the cup size have? I run a Supra SSV with about 2000# of ballast. I'm sure either will work fine however I would just like to know. Thanks...

top end. IIRC the 475 have a few or mph's than the 466. B/c of the .5" of pitch and bigger cup. something about the cup spinning water off the prop giving it more pull at high RPMs?

Karl, line 1...

In general( non cavitating props) cup acts like pitch. So, more cup is the same as more pitch. There is almost no disadvantages to cup unless prop rpm starts getting very high or you spend an inordinate amount of time in reverse and in fact more modern prop designs are 'cupped' over the entire blade and therefor don't appear to have a cupped edge.

Cup works while the prop is spinning at high speeds, but not low speeds. You can cup a prop up to about .150 on a 14" pitch prop without getting to the point of limited returns. So, if you have a prop that has low pitch for hole-shot and a lot of cup (.090-.150) you have a prop for the best of both worlds. At very high rpms (5,000+) cup loses its effectiveness. That is why the drag boat props are not cupped - they use rake (the difference between the pitch of the blade at the hub and the tip) to move water outward to the larger blade area. Our props use some rake, but not to the degree of the very high speed props.

To answer your question directly, either prop will do. The 475 will have a top end advantage of 2-3 mph but will accelerate to 30 mph about a second slower.

Thanks guys. Exactly what I was looking for.