Ranger Dave

These engines have a rev limiter that grounds the ignition system when you exceed the specified rpm (around 5500 I think). Your condition kinda sounds like the rev limiter is kicking in too early or perhaps the wire going to the rev limiter is grounding out. You might check your spark plug wires as well. I was having a some problems with idling and initial acceleration. Problem was a loose spark plug wire on the top cylinder. Since the engine idles on just 2 carbs, a loose spark plug wire on one of the top 2 cylinders can cause a momentary loss of power of 50%. Don't know why it got loose, but it has done it several times now. It doesn't fall off, it just slides up the spark plug about 1/4". It is close enough to fire the plug most of the time but will occasionally mis-fire and usually would mis-fire on acceleration as the acceleration caused the engine to shift and cause the spark gap to increase.

I have a 2002 Mercury 125 which should be very similar to yours. I rebuit my carbs last spring (part numbers below). Only the top two carbs have idle jets. The bottom two carbs only kick in about 1400 rpms. The book says that enough air flow goes through the bottom 2 carbs to keep the engine lubricated but not enough to support combustion. It kinda works like a 4 barrel carb system on a car where the car only runs on the front 2 barrels until you reach a certain point in the linkage or if you stomp on it. Take a look at the linkage side of your carbs at the top; only the 2 top carbs will have mixture adjustment screws because they are the only two carbs that have idle circuits. The reason why your outboard doesn't die while spraying cleaner in the bottom 2 carbs is because there basically isn't any gas being supplied by the bottom 2 carbs at idle or slightly above idle because the carbs don't have idle circuits. However, on the two top carbs, since they are already supplying gas through the idle circuit, the engine floods out. There is another similarity with a 4 barrel carb. Since the bottom 2 carbs don't have idle jets, on a rapid acceleration, the bottom 2 carbs will lean out instantly and cause a hesitation problem. To prevent this, your outboard has an accelerator pump that squirts liquid fuel directly into the crankcase just behind the reed valves. The accelerator pump is driven off of the throttle cam. It is a small aluminum housing with a white button on top that touches the throttle cam. According to a Mercury Mechanic that I have been emailing, Mercury messed up their parts system a few years ago when they dropped the leading prefix number. This caused some duplication of part numbers which mainly affected the early 2000 model years. The original part number for the float needle was something like 1395-9595 1. They still make this needle but the part number was changed to 1395-879194011 and it is approximately $8 each. The gasket set for the carb is 1395-811223 1 and it about $6. The "carb kit" includes all of these parts but a few other items you don't need but it is over $30. These prices are cheaper than listed on Mercury Parts Express. They are from a place in OK at www.perfprotech.com where I buy most of my parts. They are about 80% of list. You can probably get these same parts over at Center City Marine or Bass Pro Service Center at Sunset and Campbell. Do you think you have a problem just because the engine doesn't die when you spray cleaner in the carb or are you having specific problems?