My '90 Merc 25HP runs rough at low speed and I am asking if someone can help identify the cause. At about 1/8 to 1/4 throttle, the motor runs at a low rpm for a few moments, then abruptly increases in rpm without more throttle. Starts fine and runs well at WOT. I checked the spark plugs and they are oily. I tried checking the timing (with my Snap-on automotive inductive timing light) and found the timing at idle at about 1 mark left of the 0. However, the motor seems to "miss" once in awhile, and the time becomes jittery. I use a mix of 50:1 Pennzoil 2 stroke Outboard oil and gas. What is the cause? Thanks,
Jeff
Jeff