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Prop selection


eleeski
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Skoke made an interesting observation on another thread regarding how props change wakes. I wonder how much effect it has on the feel of the pull. Can a prop effectively improve the ZO pull?

My boat had a really strong pull and it was hard to get great buoy counts. Not just me, but lots of people struggled behind the boat (2004 MC with PP Classic).

I ground up my prop and replaced it with a prop with 1/2 inch more pitch. The hole shot is a bit weaker but acceptable. The trick wake hasn't changed much. The slalom wake also varies more with # of people and weights in the boat than any prop effect. But for some reason, buoy counts are better. Maybe it is the new (slightly more conventional but really long 69") ski. But Mike raved about how great his 35 felt - normally he's just getting in shape at this time of the year. Times are right on. Maybe the water has warmed up enough but it is still a lot colder than the sticky 95F water of summer.

Maybe the prop softened the pull a lot. If so would it change the feel of ZO for the better? Has anybody with a ZO boat changed the feel with a prop?

Eric

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In a word, absolutely.  Don't forget, a prop does act a bit like a torque converter, so changing the fluid characteristics will make a difference.  One could go as far as installing a multiblade prop that effectively cavitates at slalom speed, and I am sure it would feel nice and soft.  I would nickname it the powerglide prop.
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Nautique ruined its trick wake by trying to get the hull to inject air into the prop (the 200 still sucks for tricks). But the Nautique pull is nice and soft for slalom. So is a bit of prop cavitation going on with Nautiques?

Could I get the same effect by drilling a hole in the hull of my boat just in front of the prop blades that would allow air into the prop? Obviously I would need a tube to above the water level to keep the boat from sinking. I could put a valve in the tube to preserve my MC's excellent trick wake and keep a stiff jump pull when closed and simulate the Nautique when open.

Shall I break out the drill on my old MC? If it works do you think MC will give me a new boat?!!

Eric

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Baja, do you think this would be the first time I've taken a drill or grinder to an expensive piece of equipment? But now that you say that, I'd better put a metal plate under the fuel tank so I don't do anything stupid like drill through the fuel tank...

Eric

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Just route the exhaust exit to just in front of the prop, they do it in F1 to the wings and diffusers.  You also have a hole where that silly silver shaft goes through.
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Eric, just having fun. Since you make your own skis out of exotic composites I'm sure you have had many ideas that didn't perform as anticipated but that ultimately lead to breakthroughs. That's the way invention works. Drill baby drill!
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A four blade prop is generally better for slower speeds, 3 blade for faster (slalom/footing) speeds.  That is even truer today with the CNC and larger blade area 3 blades options.  The 4 blade prop tends to lose efficiency at 3500 rpm on up to top speed due to the next trailing prop being too close to the leading one.  That causes them to cavitate and lose efficiency.  Four blade props tend to be better on the holeshot but give up 1-2 mph at the top end.  So the simple answer to your question is no.  On the other hand, none of that describes what the table will do between a 3 and 4 blade unit as far as softness and froth.

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