I have a question for you: my 1987 25hp johnson motor has been running rough lately. It was running fine, about 20 mph with about 500 lbs of people and 2 gas tanks, and about 200 lbs of other stuff. It's a vhull 12ft. It suddenly slowed down and started shaking and making a lot of noise and smoke. So I shut it off and let it cool down for about 15 to 20 minutes. When I fired it back up, it wouldn't go over 4 mph. I ran it back to the ramp, then changed the plugs (top very oily and bottom very sooty) and changed the lower unit oil. Nothing happened. I put some seafoam in the gas, ran it for 5 minutes, then let it sit for about 12 hours. Not alot of smoke came out, but my son's taking it out as I'm typing this. I'll update you in about 2 hours. Thanks for any help. 