I already spaced my outer toon 3 inch. Was talking to the prop shop yesterday told him about my set up he says 8 on the center is ideal and is wanting to send me a 5 blade 17 pitch stainless. Told him I wanted to start with a aluminum 3 blade 15 x 15 with the cupping for a toon and get stats from there before dropping 400.00 on a prop not sure when I'll put the 150 on with probably need to go to hydraulic steer first . I will probably order a 13 for my 115 and use it for a while who knows
I'd be a little leery of that prop shop. How does he come up with 8" being ideal? Now it might be in your case,but as far as I know it's uncharted water. When Manitou first patented the idea they found 23"/27"/23" tubes with 5 1/4" of differential to be ideal. If I'm not mistaken they now have some up to 7". It's the angle of deadrise they were after. So depending on overall width,strake location,and tube diameters that height will vary. A 102'' wide deck with 25" outer tubes would require more height differential for "their" optimum deadrise angle. Regardless of all that optimum is dependent of what ones trying to achieve. Maybe this guy has built a pontoon himself discovering something the rest of us haven't yet,but I doubt it.
It also almost sounds like he has a 17 pitch 5 blade he's trying to get rid of. Unless he can get you another 6 mph out of your loaded down toon. It'll bite,but so will a 15"x15" three blade. I haven't tried a 5 blade,but have ran 4's on many different hulls including my toon. In every case but one I have found 3 blades that'll out run them. Most of the time by 3-4 mph. On my toon I tried the most aggressive 4 blade I've ran on a 22' wide bodied bay boat. It performed better on the bay boat then it did on my toon. That extra trailing edge on a 4 blade creates too much stern lift for my toon,not creating the bow lift needed to reduce the wet surface area at speed. It ran flat and wouldn't lift the bow. And I purposely tried to keep my bow lite. A 5 would create even more stern lift. I did find that my hunch was right on the two hulls wanting the same blade design. That is a large dia. high raked 3 blade. A 3 blade will carry the bow better,if it hooks up. The high rake angle tightens up the thrust cone,which helps with the leverage for more bow lift. The only high raked 3 in our low pitch range that I know of is the Mercury enertia. And, as others have found has good bite and is a fast toon prop. Now if your extremely stern heavy like a big block I/O or a toon with dual 300's hanging on the back the 5's might work good.
On a side note if your motor is mounted too high a high rake prop won't work. They will draw in more surface water because of the blade angle. If you can achieve 3/4 positive trim the high rake prop should work.
