An I correct or incorrect?

[boat_beginner]

I'm trying to determine what size prop I need for my boat, a 24' pontoon.
I have a 1973 85hp Evinrude on it right now, running a 13 1/4 x 17 aluminum prop, and turning at 3100 rpm WOT. I'm not to sure of the exact speed, but its abound 16.5mph, I don't have a GPS on the boat to know exactly, and don't have any plans to buy one, so that is based off an iPhone app while underway.
From what I have gathered, the motor has a 2.0 gear ratio, and should be around 4500-5500 rpm. I would like to get at least 5000rpm if possible.
I am coming up with a 9" pitch to get my at 4700, which isn't quite where I would like it to be. I have found a new prop on eBay, that is a 14x9. I considered trying it, and if its still to much pitch, have it repitched lower, but a 9" pitch seems almost to low. Am I wrong?
There is also a 4 blade, which I would much prefer, but the pitch is to much to even have repitched.

14x9
http://item.mobileweb.ebay.com/viewitem?itemId=190723937127&index=0&nav=WATCHING&nid=87020691952

4 blade
http://item.mobileweb.ebay.com/viewitem?itemId=290925597542&index=2&nav=WATCHING&nid=12502676907

There is also a 14x11 mercury prop I have looked at, but I'm not sure if I can have a different hub put in so it can fit an evinrude motor. And it is an 11" pitch, which i believe is to high, so repitch it. Does anyone know if I can re hub it to fit an evinrude? And the mercury prop almost looks more like a "pontoon" prop, with the larger blades on it too.

http://item.mobileweb.ebay.com/viewitem?itemId=321107109127&index=4&nav=WATCHING&nid=34389173393

 

[jestor68]

Re: An I correct or incorrect?

I'd say that your Evinrude must be down on power; as my 90 Merc on a 24 ft Tracker pontoon does 5200 rpm with a 15 pitch.

You will just have to prop it however you have to in order to get the rpm up within the recommended range.

If you use a Solas Amita, you won't have to worry about the correct hub kit.

Another consideration(more expensive) might be the Evinrude "Hydrus" line of pontoon props available in 9,11, and 13 pitch. They use pressed in hubs also; so no worry about matching the correct hub kit.

Buying something off E Bay and then trying to match the correct hub kit to get a Merc prop to fit your Evinrude might be exercise in futility.

 

[boat_beginner]

Re: An I correct or incorrect?

I was almost thinking the same thing at first, but it seems to run really smooth from idle up to the current WOT rpm. I'm not sure how to check to see if it is running properly or not other than just listening to the motor.

 

[steelespike]

Re: An I correct or incorrect?

Just get one of the 2 9" Solas props listed here on iboats for your motor.Read the details.
You will know it is the right prop for your motor,that it will work right and that it is a state of the art prop with a proven success history.