Just bought this little outboard. No serial tag on it. Appears to be a 6-8hp. Cleaned carb and got it to idle better after playing with the idle mixture screw. Idle speed seems low, idle screw isn't touching the foot of the throttle for idle speed. Thoughts? What about the "knock" when decelerating in neutral, is this normal? Will change plugs, no idea if gas is any good, it's what was in the tank it came with.