I have a Johnson/Bombardier 9.9 4-stroke, circa 2001. Has always run great. Now it runs great at all speeds, except when I try to idle down to slow trolling speed. It will promptly die. If I idle up a notch, no problem, but then I am trolling too fast for salmon, trout, walleye (would be fine for wahoo or sailfish!). Mechanic has decarbonized, cleaned the carburetor, changed the plugs, and fully inspected, and cannot figure it out (he can't get it to slow idle in the tank either). He said that Bombardier has made improvements to this motor since it came out - not sure how that helps me, or why it ran so well for so many years until now. Any ideas? Thanks.