What's the proper pitch??

I own a 1986 20 hp Evinrude electric start tiller. I want to increase the hole shot and get up on plane quicker. Increasing the pitch will do this, correct. Standard prop has a 13" pitch. What will this increase do to the top speed? Increasing to a 15" will increase hole shot, but what will it do to the WOT rpm's.

Re: What's the proper pitch??

Going lower in pitch will increase holeshot, you are thinking backwards. Higher pitch is gearing up so slower holeshot, lower pitch is gearing down which increases holeshot...

Re: What's the proper pitch??

What year,model and weight boat is it on?
You would probably do better if your read the stickys at the top of the prop forum.
Your motor needs to be able to rev freely within its rpm range.
It would help us get you setup if you can get us your lightly loaded wot rpm and gps speed.
A wot gps speed at the least to help get an idea how your propped.
As suggested decreasing pitch is one way to improve hole shot,also 4 blade props usually can help.
What pitch would depend on your present performance.
Careful weight placement or elimination,motor trim and height,in the extreme the addition of something like smart tabs
may help.

Re: What's the proper pitch??

It is a 1994 Sylvan Supper Snapper (with floor). On line it says the weight of the boat is 285 pounds. With my wife and I in the boat, (me..250 pounds and my wife, average weight..I wish to live and see tomorrow) WOT is 4810 RPM with a Sierra Tach and the speed is 20-21 mph with cell phone GPS. Have checked GPS speed vs car speed, very accurate. Engine manual says max WOT is 5000 rpm. Cavitation plate is flush and square with bottom of boat. Six gallon fuel tank rear starboard, battery rear port. At WOT and up on plane, the spray is coming right up beside the back bench that I sit on.

Re: What's the proper pitch??

Assuming you're running a 13 pitch now, a Solas 12 pitch and a Doel Fin will have you on plane in a jiffy.

Re: What's the proper pitch??

My info indicates that rpm range is 4500-5500, that 69-72 models were 5000.
Assuming a reasonable weight for you and your wife I come up with about 900 lbs for boat,motor people and gear.
A good chunk for a 14 footer. That may account for some of your really high slip of 37%.
Is the prop from 86? A bit worn and kind of thick blades?
I'm thinking that a 11" 4 blade Solas prop should improve your rpm and slip numbers.And improve hole shot and possibly speed.
Not that jestors suggestion is wrong it could be vary effective.I like the Doelfin and have had good luck with it but consider it kind of a bandaid over a problem.In this case maybe your problem is unavoidable weight.
Now a bigger boat might help the weight problem too.
I had a bare 18 ft Crestliner utility with an old 25 Gale in the 70s. It planed easily with 6 adults aboard.
The 25 on a bare 15 footer struggled to plane 4 adults.

Re: What's the proper pitch??

I do have the stabilizer fins on the outboard. Spun the hub on the prop last year and replaced it with a 10.5 " x 13" standard aluminum prop. I obviously had the whole pitch idea backwards. So your saying a 10.5 inch prop with a 11" pitch will give me a better hole shot, higher rpm but may loose some top end speed. A higher pitch, say a 10.5 inch prop with a 15" pitch will loose on the hole shot, possibly gain a little top end but may also load the engine down. I had it all backwards. Thanks for the lesson steelspike. I hope there aren't any tests.....I've never been good at tests. Also thanks to jestor68. This iboats forum is unbelievable with the help and information that is available.

Re: What's the proper pitch??

Good luck let us know how you do.