Early 80's 15's had on the plate operating range 5500 to 7000. 15 hp produced at 6250. I understand that this 7000 rpm on this motor is the highest rpm ever produced on a non-race outboard. Anyone know if this is true??? I need to get on plane fast in real shallow water or scrape bottom with prop. Will this added 750 rpm help? Only good for light loads? I currently have a 9.9 that I added the 15 carb to. I use a 12 inch prop that is the largest I believe. It seems to do good, but I don't believe it is quite 15 hp. Do you think the 7000 rpm motor with the tuned exhaust they have make more than 15 hp? Anyone know why they stopped making the 7000 motor? I have seen a few of them and they still run fine and have high compression. Some say to run 40:1 at 7000. I use synthetic oil. I also have a 1999 Mercury 15 that is almost new and I can't run til spring coz lakes are frozen here. Anyone know or guesstimate how the Johnsons and the 15 Mercury compare on power/speed with similar props?