Why is my red wire dead?

[laxrebel]

I was working behind the instrument panel of my pontoon (when I forget to turn off my master battery switch!) I sparked the red wire to ground and lost power to both the instruments and the ignition feed. I checked and replaced any of the battery cable and engine blown fuses (one was blown) but I still I have a dead red wire to the ignition switch. All four fuses on the engine test fine. Battery cable fuse was replaced. As a test, I've jumpered from another good power lead to the red wire terminal on the ignition switch and now the engine starts and runs, so the red wire from the engine to the ignition switch is good and I have all other power (gauges, etc. but of course my lights master power is now energized with the switch off.) So it seems like the battery line to the engine is bad (why now?) or there is another fuse somewhere or something on the engine battery connection is toast. Ideas? Engine: 2005 Mercury 60hp ELPTEFI on a 2005 Monarch pontoon. Thanks. I'm stumped.

 

[Scott Danforth]

Fuse at battery or under cowl on motor?

 

[laxrebel]

There are four engine fuses per my Mercury manual and I've checked them all. The one that was blown was for the "main relay/accessories". Checked them all including the battery cable fuse and all test good. I can find no fuse under the dash, and there usually would not be one on the main red hot ignition wire. The confusion is that if I jumper to the "dead wire" red tab on the ignition switch the motor starts and runs, which to me seems to mean that there is no power going to the motor from the battery cable downstream from the fuse or at the engine where the cable connects, and thence to the ignition switch and start/run circuits, since all the engine circuits and components are powered by the jumpered feed and all work correctly. The hot red should feed power to the ignition start and run circuits when the key is turned. But I can't see a problem with that either. The ignition switch is good since the engine starts via the key when jumpered. Also, if I leave the jumper on at the ignition switch but disconnect the "dead red" wire the motor turns over but will not start, if I reconnect the dead wire the engine starts and runs, so the red feed to the other tabs is good. It seems that it must be something obvious since I just sparked the connections and blew the fuse. No dead short involved that I assume could have fried something. But at this point what is wrong escapes me. I hate to have my marina pull my boat ($$$$) if this is something I've simply overlooked or am confused, per above. Can a fuse test good but actually be dead? I'll try replacing all the engine fuses and see if that cures the problem. Thanks for the support.

 

[laxrebel]

Problem solved! The first thing I did when I blew the fuses was to replace the blown one and check all the others. That did not solve the problem. After hours of checking things without result I felt the problem had to be on the engine somewhere. As a guess, I pulled all the fuses and replaced them. Pulled the jumper. Turned the key and the damned thing powered right up. Rechecked the fuses. The 20 amp mini for the master relay tested good until I wiggled the tab and it moved - then tested bad. Bad fuse. Lesson learned. Thanks for listening.