I have a 1997 Johnson (on 15 Whaler) that has run great, but starting bogging out of the hole and on turns while pulling skiers, but would then re-catch and go. It became more pronounced, so we chnged fuel filter and it seemed to go away. Then it came back worse to where the boat wouldn't plane at all. So we tried a new filter again with fresh gas and it still bogged eveb without skiiers. Then I noticed that I could get it to pick up rpm's by pushing in the ignition choke switch. It ran for a couple minutes then died. I also noticed a fuel slick around the engine when I paddled back to the dock, but thought this may be excess gas from flooding. Any ideas?