2002 Mercury 50 elpto won't rev up

[cannon650]

I have a Mercury 50 elpto that is hard to start sometimes and won't throttle up. Other times it will start right up and run fine for ten minutes or so then it will bog right down like it is getting to much fuel or not enough. I cleaned the carbs, checked the fuel filter and cleaned out the fuel tank,everything looked good.I'm only the second owner of the boat,the first owner never used the motor only the electric motor.I bet I haven't even put 5 hours on the motor. I bought the boat in 2008 and never had a problem until this year. Any ideas on what's causing this would be appreciated.

[Ski]

Sounds like ethanol problems. Check to see if the spark will jump a 3/8" gap. (while your cranking it check the compression for grins) Make sure the other plug is touching ground or you'll wreck the coil. If the spark is good, install new plugs to rule them out and take it to the lake. Advance the throttle to where it's bogging down and shoot the carb with starter fluid. (light shot should do it) If it's speeds up, order a new carb. The ethanol eats the small passages in the carb and changes the diameters choking off the fuel.

[cannon650]

Thanks for the reply ski,I just got to working on the motor again.Spark is good, put in new plugs,went through the carbs again,not a trace of corrosion anywhere.Tried the starting fluid no difference.Pulled the plugs again and what I noticed was the last time I pulled them the top plug was dry,the other 2 were wet. This time I pulled them the bottom plug was dry and the top 2 were wet.So I checked the wiring and found that the wires that come from under the flywheel where tied together on top of the engine and one of the wires burnt through the plastic connector and was touching the top of the engine. I put on a new wire connector and the motor fired right up and purred like a kitten.I hope that was it, I'll know more when I get back to the lake. Thanks