1990 20' Lowe pontoon with same year 40 hp Johnson. Motor seems to run fine but at times at 4500 - 5000 rpm if feels like the toon is spinning its tires. I take a look at the motor when this happens and looks like not a lot of water around prop. I tilt up and down and I may get a little more bite tilted down. I tried to pull a tuber and just seems to spin all the time and can't get traction. We've gps and at around 5000 rpm we are going 13 mph. That just seems a little slow. Now a few weeks ago at very slow speed I did hit something that put a small rip in 2 of the blades so MAYBE I've spun a hub. So I plan order a new hub and at "Propellers 101" they suggest a 3 blade 12-1/4 x 15 for top speed and a 12-1/2 x 13 for heavy loads and tubing, which we really don't do that much. Does anyone have a good recommendation on prop size? 3 blade? 4 blade? And what speed should I be getting out of that 40 Johnson on the 20' toon? Usually only 2 to 5 people on boat. Toon is new to me this year so we've only had it out a few times before I hit whatever it was. Damn Lake of the Ozarks just can't keep a consistent water level. But our maiden voyage I don't remember feeling the "Spinning tires feeling" so maybe its just a spun hub. But we still only got 13 mph with 4 people.