I have a 1984 Merc 70 HP that ran fine until I filled up with fuel at a local marina. Shortly there after it began to smoke and lost power. I drained that fuel and put in new with no better luck.<br />I took it to a local mechanic who said the CDI box was the problem so I changed it myself. I refueled this spring with premium fuel this spring and took it to the lake. It started poorly and has no low end power. It fluctuates in speed until you get it up to full throttle. Once at full throttle it runs fine and seems to be at the same top speed as it was before the problems. In checking the plug wires while it was running I recieved a nasty shock from plug wire #2. I know that it is firing on all 3 cylinders as I pulled off each plug wire and started it up with 1 at a time. Most people say it is a fuel problem but a few suspect the plug wire is causing problems. I am not sure if the CDI box had anything to do with the problem or not. The mechanic said he tested it and determined 
it was no good. Thoughts?
it was no good. Thoughts?