93 Mercury 40hp outboard- no start

Greetings to all- been lurking and searching for a clue to my delema. My 93 Merc has given me several years of trouble free use...untill last year. My brother had it out for the usual fishing run- traveled to the "spot" & went about his afternoon. When the time was right he went to fire the engine and all it would do is crank, no spit, no spudder- nadda. I was a diesel mechanic for several years so I proceeded to check for spark on all plugs (had spark, but I would call it weak) checked fuse- ok, gave each cyl a squirt of fuel and tried it- nothing. In searching thru forums and repair sites I see that it is somewhat common for the switchbox to fail. Anybody have a "test" for it as I really dont like to throw parts @ something and hope for the best. Thanks in advance.

Seve

Re: 93 Mercury 40hp outboard- no start

Before going any further, if the carb or fuel pump is not functioning the crank case may be totally dry and no fuel is getting up to the combustion chambers. Are you showing fuel on the plugs? If so then put new plugs in. They may not be firing under compression. If none or little fuel on the plugs shoot a bunch of fuel mix into the carb throat whilst turning the motor over. If still no fire then use a spark tester to check the spark strength. If sparks are there but weak check the cleanliness of the plug wire terminals. A resistance check of the plug wires may tell you something. It is not unusual for the plug wire connectors to corrode in the wires and produce bad connections. It is not unusual for corrosion of the coil connections to produce bad sparks.

Re: 93 Mercury 40hp outboard- no start

James R said:

Before going any further, if the carb or fuel pump is not functioning the crank case may be totally dry and no fuel is getting up to the combustion chambers. Are you showing fuel on the plugs? If so then put new plugs in. They may not be firing under compression. If none or little fuel on the plugs shoot a bunch of fuel mix into the carb throat whilst turning the motor over. If still no fire then use a spark tester to check the spark strength. If sparks are there but weak check the cleanliness of the plug wire terminals. A resistance check of the plug wires may tell you something. It is not unusual for the plug wire connectors to corrode in the wires and produce bad connections. It is not unusual for corrosion of the coil connections to produce bad sparks.

Click to expand...

I had ok spark (by looking @ he plugs when cranking- I would call it weak by sight only). I threw a set of plugs @ it just because I had never changed them in the 4 yrs Ive owned it. I gave each jug a good dose of gas mix w/ new plugs- never even popped, just cranks and cranks. Plug wires may be an idea, but they (along w/ everything else under the hood is dam near spotless.) granted that mean nothing as I've been burned by "It looked good" in the past. I guess I can see if the plug wires had/have corrosion, but to not have it fire, pop or spit @ all? Ran perfect right up to that point. Your comments are always welcome. Thanks for the reply.

Steve

Re: 93 Mercury 40hp outboard- no start

Might be helpful

http://issuu.com/cdielectronics/doc...t.xml&backgroundColor=000000&showFlipBtn=true

That's the CDI Electronics troubleshooting guide. Browse till you find your engine. It contain a very detailled troubleshooting procedure.