Launch prop talk.....

[DAFF]

So here is my ??? Have a ss 4 blade on the Launch, not sure on the model number or make. But during a hole shot the prop seems to slip in the water more than the older Sunsport. The Idle to 4000rpm and the boat is barely moving yet and you can red line the engine almost instantly. NTM the water it moves is insane. Cruises around 22mph at 2800rpm too. Is this about right ???

I am leaning more top end than power out of the hole for the kids are only 8-10 and I rarely get behind the boat these days.... We do love our afternoon cruises after sitting in the bay playing witht the blue gills....

Perhaps a higher pitched prop to go with the power one. One for playing and the other for saving fuel....

[relyt]

Daff.
I have been learning alot lately about props! I hav a 99 legacy that I brought from Texas to Utah and of course there is abig change in elevation. In doing so I had to rejet my carb and go from a 13x13 to a 13x11.5 .060 cup because I had no hole shot and bad top end. I have a 3 blade. I know going down in pitch 1 inch will raise rpms 200. I also know that cup helps with grab but not sure how.And by what I understand mph should be close rpms depending on your gear ratio... At any rate I think you could go up in pitch a little to get some more grab. If you contact Acme props they will tell you what you need to get to your desired power range. it would be helpful to look at the prop and let us know what you are running I am sure some of the four blade launch guys can chime in also.
Good luck!

[wiatowski]

use this to play around till you find what you want.
http://www.go-fast.com/Prop_Slip_Calculator.htm
I usually start by calculating prop slip at 12% , however my bayliner was only like 6. But read the prop slip page and it will tell you how to do an accurate test.
Once you know the slip % then all you have to do is adjust the pitch until you get your desired result. This will give you a good idea of what you would like, but I would still consult a prop store or specialist before you buy.
Note that for a cupped prop you need to add 1% to your pitch. so a 13 becomes a 14.