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View Full Version : 12' or 13' prop on an MCX?


madmax
10-01-2005, 02:15 PM
Hello,
My X-7 MCX came with a 13' propeller, can someone tell me the pros and cons if I put a 12' prop? (Beside getting a smaller slalom wake)
Thanks for your help.

PendO
10-01-2005, 07:02 PM
Hello,
My X-7 MCX came with a 13' propeller, can someone tell me the pros and cons if I put a 12' prop? (Beside getting a smaller slalom wake)
Thanks for your help.

Someone else will undoubtely know a lot more than I, but ... if you go to the 12' pitch prop you will have more holeshot, less top end ... your 13' pitch prop theoretically travels 13" in one revolution, 12" for the 12' Pitch ... if both shafts were spinning at the same rate the 13' pitch will be faster ... however, it is easier for the engine to turn the 12' prop b/c it is smaller (imagine your mountain bike, on the front you have 3 chainrings, biggest is the toughest to turn, smallest is the easiest to turn-hence you use it to climb hills, however, when you get on the flats with a mountain bike you dont want to be in the small chainring in front as you will just spin and spin and not go very fast) in principle when you get to Wide Open Throttle (WOT) with the 13' prop you currently have your engine is operating in the 4800-5200 max rpm range, if you put a smaller prop on you run the risk of "over-revving" the engine at WOT, and you will also have a decrease in top speed.

If you don't mind the drop in top end, and you are mindfull of not going beyond the max rpm range you may enjoy a smaller slalom wake - I'd be interested to know since my 197 has MCX with Powerslot has the 15 pitch (a different discussion though as it needs the larger pitch to compensate for the 1.26:1 gear reduction).

JDK
10-01-2005, 07:37 PM
(Beside getting a smaller slalom wake)
Thanks for your help.

I think you might be mistaken. IMO, less pitch = more rpm on the prop to get to the original speed = more turbulence behind the boat.

..... this is assuming you are referring to going to 12" pitch and NOT 12" diameter.

madmax
10-06-2005, 01:18 PM
Thanks guys, you are very nice and helpful. But I'm a little confused, does it mean a (smaller)12" prop would make a bigger or harder slalom wake??

PendO
10-06-2005, 05:50 PM
BUMP .... IMO (very limited, I might add:)) the 12 pitch prop would make a smaller wake than the 13 pitch prop ... but at equal velocity the 12 pitch IS turning more RPM's than the 13 pitch prop ... I belive JDK is right that you may have more "turbulence" in the water, but the size/height if anything is smaller with the 12 pitch as compared to the 13 pitch (so long as you are comparing two props from the same Manf. - i.e. Acme to Acme ... OJ to OJ) Also, I'm not skiing buoys, so hopefully someone who does can confirm or set me straight.

I'd email Acme or OJ as they will be able to compare their own props to one another ... and some have a try before you buy (they will let you return for credit) policy.