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#10859195 - 05/20/15 05:32 PM Prop education. School me on the numbers
Biscuits Offline
Extreme Angler

Registered: 01/18/06
Posts: 2545
Loc: Medina Lake Tx
I have zero idea what pitch and cup does for a prop. Let's use my boat for example. I have a 86 skeeter 18.5 ft with a manual Jack plate and 1984 150 Rude. My prop is 14 1/4 X 21. I like to save gas so don't really care about top end mph. I run around 4500 to 4800 max but the motor does around 5600 WOT. Hole shot is more important to me.

I am not looking to change my prop, I am very pleased with the set up the way it is. I just want to know what the numbers mean. What happens if I got to a 19 pitch or up to say a 23 pitch? What will cup do for me? Say I wanted to get max MPH out of the motor, what do I do? Ed-u-mi-cate me please.

Current Cylinder Index is 42.

#10859366 - 05/20/15 06:52 PM Re: Prop education. School me on the numbers [Re: Biscuits]
Pat Goff Offline
TFF Celebrity

Registered: 01/29/05
Posts: 5264
Loc: Marble Falls/Seadrift
Pitch is like gears in your truck. It's a theoretical number of how many inches it travels for one revolution. Your prop in a perfect world would go forward 21 inches every turn it makes.

Now to make it confusing nobody can achieve zero slip so the fun starts. 12% is a good slip number for most bass hulls, really light and efficient boats like an Allison get a bit better.

Cup helps the prop work more efficient by grabbing a bit more water, especially when you start elevating the prop tips out of the water.

Now that all sounds pretty simple, right? It isn't. There's few really good prop guys that know exactly what they're doing, most can ruin that $500 wheel forever. Steve at fork is one of those few.

Some props beg for attention including but not limited to: all rakers, even pitch tempests, and lazers. It's amazing what a difference a skilled hand can make on them.
Pat Goff
Marble Falls/Seadrift TX

#10863237 - 05/22/15 07:51 AM Re: Prop education. School me on the numbers [Re: Biscuits]
steve@hydrodynamics Offline
TFF Celebrity

Registered: 08/25/06
Posts: 6777
Loc: Quitman,Tx
thanks Pat. we work our tails off here improving props and a boats performance.
it's not easy as there alot of unknown variables that come into play on every
single boat.

24 years later and i'm still learning. it's just fun and it's what we do here.

#10870492 - 05/25/15 09:17 AM Re: Prop education. School me on the numbers [Re: Biscuits]
John175 ® Online   content
Super Freak

Registered: 10/21/05
Posts: 65721
Loc: Realville
Steve B&B's and added cup to my props. Massive difference between a properly worked prop and a prop out of the box.


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