Last weekend we used a most unusual spring like day in North Florida to take the boat out on Rainbow River. When I started the motor I immediately noticed it sounded like it was running on one cylinder. I let it idle cold for a few minutes and then I could hear the second cylinder start to fire. I thought “well that’s strange but let’s give this cruise a shot”. The entire river is a no wake zone so idle speed the entire 5.5 miles with a max speed never exceeding 4.5 MPH. The motor seemed ok but after about 20 mins of run time the motor began to intermittently switch from running on both cylinders to one and back again. I adjusted the mixture screws until she seemed to smooth out, but alas… that was not the case. After about two hours of this back and forth misfiring we turned around and headed back to the launch site, putting along on one cylinder for about an hour. Any ideas on where to start?

Full disclosure: About a month ago I replaced the coils, plugs (J6C plugs gapped at 30), plug wires, cleaned & filed the points and set timing with a multimeter. I also took the runaway cutout switch apart to see the condition of the diaphragm and it looked great to me. The motor has also been converted to a single line fuel delivery system and new pump, using Sierra part # 18-7352. Motor runs great at WOT and shows 120psi on both cylinders.