removed the loose sheet metal baffle plate that has been banging around inside the valve cover for who knows how long! 

I had never had the covers off until now.

The rocker arms have been hitting the sides of the filler/breather baffle plates. The left side actually broke off the spot welds holding it onto the valve cover and it's just been getting the crap beat out of it for some time. 

This boat stuff just never stops.