Air, Fuel, Spark?

So this will probably be almost impossible for anyone to diagnose without looking over the engine in person, but it's worth a shot. So we were out on the lake today, the 1988 johnson 140 fired right up and ran smooth for about 5 minutes at "no wake" speed, and then for about 2-3 minutes at WOT or close to WOT. Then the engine started bogging down and we lost significant power. Then after 30 seconds to a minute of not much power, the engine shut off completely. After removing the cowling, I found a a family of mice had made a home out of my engine. One mouse was recently dead, fried probably, as its teeth were around on of my spark plug wires. The wire was pretty chewed up, but there was some wire left, so I wrapped it with electrical tape. after examining the rest of the engine, I couldn't find any other wires that had been chewed. The engine still wouldn't turn over though. So I narrowed it down to the three basic components of starting a motor; spark, air & fuel. I believe I took care of the spark problem with repairing the one wire. Our next thought was that the mice had made their nest some where which would restrict the flow of air into the engine. I'm not sure where that would be though? I presume outboards don't have air filters, so how does the air get to the engine? It could be entirely unrelated the the mouse problem and be fuel. The fuel we have here has ethanol in it, but I did treat it with stabil Marine after filling up this morning. Anyone have any possible ideas what the issue could be? The engine cranks when I turn the key, but the starter motor just spins, it never turns over. Thanks

Re: Air, Fuel, Spark?

Depending on the wire, maybe something else could have been shorted out. I don't think electrical tape is a good enough insulator for any ignition wire. They arc out of the end of good plug caps easily enough, so replace the wire that's chewed. If it's the coil wire and not the spark plug wire you maybe have to replace the coil pack.

If you had mice in your engine eating wires no telling what else could be wrong. I doubt they could fit through the air silencer gills and get into the carbs but you never know. I can say I have learned that dirt, grime, or foam (from engine hat) can easily be sucked into the silencer and cause idle jets and stuff to get clogged. So if you had mice nesting you could have sucked debris in somewhere you don't want.

Someone else might have some 2 cents.

Re: Air, Fuel, Spark?

Thanks, I will replace the spark plug wire for sure. As for the silencer/idle jets and such, how do I access them on my motor? Thanks again

Re: Air, Fuel, Spark?

I removed the plastic cap covering my carbs, and everything seemed fine in there. Are the vents on the side of that plastic cap the air intake? or is that somewhere else on the engine?

Re: Air, Fuel, Spark?

with an air gap spark checker <~$6 at most auto parts places > determine if you have spark to any cylinder... set spark gap at 7/16"....motor needs to spin ~250 rpm to activate ignition system...if spark exist...fuel supply is next...pump bulb up and go through routine starting procedure....all testing should be done on muffs or in the water to protect the water pump impeller

Re: Air, Fuel, Spark?

Thanks guys. I replaced the spark plug wire, added more sta-bil and cleaned up the motor a bit. Not sure what the problem was, but the motor started today. I don't believe it was the spark plug wire because wouldn't the other three cylinders still fire? Anyway, it started so I guess I can't complain.