Why prop changes?

[handleandrew]

According to the MC owners manuals a 2003 197/x7 and 209/x9 with MCX motor and 1:1 transmission both take a 13"x13" prop. Meanwhile a 2005 197/x7 and 209/x9 with the same MCX motor and same 1:1 transmission both take a 12.5'x12" prop. The hulls were unchanged during those years. Any idea why or what the difference would be? Any input is appreciated.

[FoggyNogginz]

Likely just preference over time. I ran a 13x12.5 on my 2003 X9, which is oddly called the Acme 209. That was my favorite prop for slalom and surfing. What prop is optimal for a boat depends on a lot of things, including whether or not you're adding ballast, want to optimize for holeshot, smaller table, elevation, etc....and of course what your RPMs are at wide open throttle.

The manual will tell you what propeller Mastercraft recommended at the time as a general place to start, but to be quite honest I don't think anyone should ever buy one of these boats without trying two or three props to determine the optimal performance for their individual situation. In my opinion (which is totally free), trusting that a boat manufacturer has put the optimal prop on the shaft for your individual situation, is a lot like assuming that the tires which originally came on your car are the best possible ones that you can buy for your driving style. I've owned four MCs and I have never found the factory prop to be the one that I felt was optimal for my intended uses and preferences.

I'd suggest either calling Jim Thelin at Acme, or Eric at OJ and getting their direct feedback for your boat. Make sure and tell them what your wide open throttle RPMs happen to be, and what you would like to optimize about the wake and performance (i.e. slalom, surf, etc) This way they can help you make an educated guess and potentially try a different prop or two so that you can make the best decision for yourself. I'm an ACME fan, but lots of folks on here like OJ too.

Good luck.

[MC25]

It’s like different gearing in a vehicle. A truck with 3.08s May work for some, but 4.10s may work for others. Top end and lower RPMs vs better pulling power at the cost of higher rpms.

[james_shoemaker]

My old S&S came with the stock prop (14x18 3 blade), I don't care much about top end so I replaced it with an acme 537 (13.5x16 4 blade), smoother and way more hole shot and easier control at the slow speeds we usually ski.

[Miss Rita]

According to the MC owners manuals a 2003 197/x7 and 209/x9 with MCX motor and 1:1 transmission both take a 13"x13" prop. Meanwhile a 2005 197/x7 and 209/x9 with the same MCX motor and same 1:1 transmission both take a 12.5'x12" prop. The hulls were unchanged during those years. Any idea why or what the difference would be?

I wonder if the 2003 specs were for an OEM old-fashioned cast prop, and the 2005 spec was for a CNC prop.

The CNC props are much more efficient.

My OEM prop with my '92 was a 13 x 13, I replaced it with an Acme 543 which is 13 x 11.5. The Acme is much faster out of the whole, no loss of top end.

[88 PS190]

I think Miss Rita has it - 13x13 really tells you almost nothing about a prop. Diameter and pitch don't tell you,

cup, volume of the blades, number of blades, surface area, on and on. A 12.5" and a 13" prop are in the same size size group.