Thick rag with solvent (acetone). Screw/twist the surface till the brown stops showing.
I never killed a set of plugs. Have heard reccomendation, change every 3 years or 300 hours, which ever comes first.
Been following force/chrysler forum for years. Surface gap plugs trolled for extended times will foul.
Plugged recirculation system will cause performance issues and excessive smoking.
Bang could have been submerged object. Shutter could be spun prop. Magic marker a straight line accross the hub. Run it and see if the line stays intact.
Bought the same combination about 10 yrs. ago. Needed transom and floor/deck work. Recommend compression test and very thurough inspection.
Did double my money on resale. My labor was free
