# Cupping a Prop



## Guest (Apr 6, 2007)

If you want to add significant cup, you have to lower the pitch of the prop to maitain RPM.   This is the reason I am going to take a pefectly good prop, cut off the blades and have them rewelded at a LOWER pitch so that I can cup the living sh-t out of it.  Expensive, but it's what you have to do with these small motors to jack them up.  It also expalins why I have an inventory of 4 blade props. 

It has been my experiance with Solas that the blades are larger, more surface area, than say Mercury or even Power Tech props which will make them more sensitive to dropping RPM's with cupping.

The amount of cup you can add will depend on your current RPM with the prop you have and how much top end you are willing to give up when you start dropping your pitch. If you want more cup, you will have to give up pitch.  For the most part it is experimental but can be dialed in pretty quick with an experianced prop man.


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## Guest (Apr 6, 2007)

It's not worth it, do not cup your own prop because u got to have a right equipment like curve stone and 20 lbs hammer. I have worked with Ron at central florida prop to help him out to work on my 4 blade prop.

If your motor made by yamaha then I highy suggest you go over to CFP and ask Ron for yamaha 30 SRA 4 blade prop 11 inch pitch with heavy cupping to fit your motor. If your shaft has a 10 tooth spline then it's good way to fit in. Give it a try. Or.u want to try one of my 4 blade prop


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## Guest (Apr 6, 2007)

> It's not worth it, do not cup your own prop because u got to have a right equipment like curve stone and 20 lbs hammer. I have worked with Ron at central florida prop to help him out to work on my 4 blade prop.
> 
> If your motor made by yamaha then I highy suggest you go over to CFP and ask Ron for yamaha 30 SRA 4 blade prop 11 inch pitch with heavy cupping to fit your motor. If your shaft has a 10 tooth spline then it's good way to fit in.  Give it a try. Or.u want to try one of my 4 blade prop


X2


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## tom_in_orl (Dec 9, 2006)

I like to tweak stuff. Yeah, big surprise when you know I have a lifted CJ7 and a couple of customized bikes. I probably would not be into forums like this one if there weren't a bunch of people customizing their microskiffs. Fishing reports are great but I check what people have posted in hopes of finding more. So I left out one step ;D I needed to back off the pitch before adding cupping. At least the cupping worked . I don't think I wasted my time and I never like taking things to anyone else unless I have proven that its beyond my own capabilities. ;D 

I may have to change my signature. I like this saying.

"I have never failed at anything. I just spend lots of time proving what doesn't work"

I may have heard that from capt'ron


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## tom_in_orl (Dec 9, 2006)

> .u want to try one of my 4 blade prop


Yes please. I did not realize that you had a 10 spline shaft also otherwise I would have asked before. I have baseball games on Friday at 6:00 PM and Saturday at noon. Otherwise I am free all weekend.


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## Guest (Apr 6, 2007)

> "I have never failed at anything. I just spend lots of time proving what doesn't work"
> 
> I may have heard that from capt'ron


Wish I could take credit for this one. :  It definately fits me. 

Quote: Forest Gump - "I like it - I like it alot". 

You could always use the "I'll either fix it up or F it up so bad someone else will find it a challenge too". ;D ;D


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## gheenoeguy (Mar 27, 2007)

I have a 1991 Mercury 25 HP with the original prop on my Classic. My prop has a few dings but is running at the same speed as when I had no dings. I'm running 29 MPH with 1 person and 27 MPH with 2 people. I keep hearing about Classics running at 33 or 34 MPH. I would like to buy a prop off the shelf but I'm not sure if I'm going to get more speed out of my motor. If I were to buy a prop off the shelf what pitch prop should I buy and what brand?


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## tom_in_orl (Dec 9, 2006)

Hey gheenoeguy,

I hear you. First thing you should know is that 29 mph solo is a good speed for a 25 HP motor. You may have 1 - 3 mph more depending upon how its set up. BTW, Just so you know I have a 30 HP motor but the new Yamaha 25 HP 2 smokes are just as strong. Somewhere I think they changed the horsepower rating system and the new motors are a bit stronger than one you have. But I could be wrong. I am just speculating on that one.

Back to getting the most out of your motor. Lots of us are weaking our stuff around here. To get more out of your boat you are going to need to follow some basic steps. I will start a new thread where we can put a good step by step process to getting the most from your motor. Its going to be a popular thread......


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## tom_in_orl (Dec 9, 2006)

I want to say THANK YOU to whitesnook for bringing out his 4 blade power tech for me to test with on Saturday. The results were awesome. I could jack the motor up 5 - 6 inches and still have a good bite on the water. I finally had to stop going up because I was begining to lose water pressure.  I was running 29.5 mph on the gps when I put the motor back down to the sweet spot. By running the 4 blade I was giving up a bit of top end but the launch was amazing. 

I will be ordering one soon. Especially since I bent another prop on the wekiva today.  I hit a submerged log while moving at fast idle though the spot called deep water. It was my aluminum prop. It was damaged so bad that I had to do emergency repairs. I stopped on a nearby island and crudely hammered it into shape over a cypress knee.  Worked well enough to make it back to the ramp with a bad vibration.


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## Guest (Apr 9, 2007)

U're welcome, I'm glad this works out really well for your motor and boat. Wekiva river is getting lower so I had to hop over the log on the way to wekiva falls. [smiley=thumbdown.gif] Logs suck!!!!


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