I am working on my 95 yanmar 3jh2e. It has just 1750 hours. I have taken heat exchanger/exhaust manifold off and can see small metal particles in the exhaust ports for 2 cylinders. With the most bits in farthest aft cylinder less in the next forward and none in the forward cylinder. Engine seemed to be running well. However previous owner had raw water hose to elbow fail and pump seawater over engine. I pulled engine to refurbish and address electrical and rust issues. Anybody know what this might mean, how serious it is? Thanks for any insights.