rust on spark plug

[toddr5516]

I seem to recall reading in one of these forums that if rust is built up on the spark plug that it means the plug is not sparking well.
I have a '73 chrysler 45 hp and the lower plug is corroded up , but the upper plug looks fine and the motor seems to be running fine . I've never changed the plugs and problally will do so tonight. Is there truth in this about rust build-up?

 

[roscoe]

Re: rust on spark plug

If it is rusty, it won't spark well.

Has the motor been sitting a long time?

Rust is caused by water.
There should be no water in there.

Also, on a 2 stroke, there should be plenty of oil in the fuel to prevent rusting.
Something is causing that rust.