Strange Arc while adjusting idle rpm screw (merc 5.0L MCM thunderbolt IV)

[dynasty_71]

• I was adjusting the idle rpm spring and my pliers I guess touched the side of the carb (I think) and it arched. Nice big spark, engine kept running, but seemed really odd that their would be anything energized in that area. I should have put my volt meter to it, but I packed everything up before I thought about that.
  
  Also.....any thoughts on this, recently purchased the boat, ran great during the assessment but after a few runs on the water, i started seeing a power loss. Boat struggled to get on plane, and only with WOT and someone sitting on the bow can I get it to plane, but its still not hitting top speed and my max rpm is about 600 rpms low per the manual.
  
  Started troubleshooting the engine, and first saw arcing on the ignition coil from positive to the tower. I cleaned the terminals because they were pretty rough, took it out and it ran great until we started heading back to the ramp. I decided to just eat the $50 and get a new ignition coil. Replaced the fuel filter, checked the fuel for water, looked good, but hte top of the fuel filter paint was bubbling which seemed odd. Figured it would be due to heat, but the engine is running cool and within range. Anyways replaced it and keeping an eye on the new one.
  
  I replaced the spark plugs today which I believe will help. One of the plugs wasn't screwed in that tight. I didn't have to break it with my ratchet, I was able to initially hand loosen it so I'm hoping when I get it back on the water, that might have fixed the loss of power.
  
  Any thoughts on the arcing and also the loss of power would be greatly appreciated

 

[alldodge]

I was adjusting the idle rpm spring and my pliers

Where is the spring?

The spark would probably come from plug wires and from the sound of it a coating of oil and crud on the motor. Wires are leaking and some of it is tacking along the surface

 

[dynasty_71]

The spring is on the port side of the carb just below the air filter/flame arrestor and between the carb and the throttle cable connection. The plug wires aren't close to where it is, they are run down the back and to the sides of the engine, but I guess they could be getting power up there. I'll try and clean off the area as well to clear off any oil there as well.

Im most likely going to replace the wires as well since there was arcing on the old ignition coil. The plugs were definitely old with some carbon fouling so I'm hoping that will help some as well

 

[QBhoy]

That’s not too clever if it’s happened in that area. Check your ignition system and earths.