Our friend and longtime OMC Tech, Joe Reeves, has posted thousands of answers to technical questions about Johnson and Evinrude motors on our Boat Repair Forum. He started contributing to the forum in 2001 and is still at it! He has helped countless visitors solve their engine problems. Here are his thoughts on Hesitation and Bogging Down On Applying Throttle
(Hesitation/Bogging On Applying Throttle)
This is a common problem and is usually caused by a sticking timer base under the flywheel or fouled, clogged carburetors, however… also check the carburetor linkages, compression, spark, and the timer base as follows.
Carburetor Linkages: Check the carburetor throttle butterfly linkages that lead from one carburetor to the another to see if they’re adjusted properly. They should be set so that at idle, all butterflies are absolutely closed. You do not want to have one slightly open at idle while the others are closed. Also, all throttle butterflies should close and open at the same time.
Compression: Normally have all of the spark plugs removed BUT if the Bendix gear kicks out of the flywheel constantly install all of the spark plugs excepting the cylinder you’re checking at the time. What are the individual readings?
Spark: With all of the spark plugs removed, rig a spark tester so that the spark has a 7/16″ gap to jump. The spark should jump that 7/16″ gap with a strong blue lightning like flame… a real SNAP! Does it?
Timer Base: With the engine NOT RUNNING but in forward gear, have someone advance the throttle slowly from the idle position to full throttle while you observe the timer base. It should advance smoothly throughout that travel range. If it sticks, find out why and correct that restriction.
If all of the four area above are okay, and especially if the engine has been sitting for some time, remove, clean, and rebuild the carburetors using complete carburetor kits. Even if you’ve rebuilt them yesterday, it’s possible that you’ve overlooked something.
Pay particular attention to the fixed brass high speed jets that are located horizontally in the bottom center portion of the float chambers (way in back of the drain plug). Make sure that they are absolutely clean. I recommend that they be cleaned manually with a piece of single strand steel wire as soaking in cleaning solvent really doesn’t do the job properly at times.