"Pratically pure copper is use
"Pratically pure copper is used for the heat exchanger tubes, oil cooler tubes, and a few sealing washers here and there. It has a finite life in a salt environment, but its a far cry better than many other, popular materials. It is very bad against aluminum, and that is maybe why jeff gives it a bad rap. As a sealing washer against steel and iron, it works fine, and is soft enough to seal. You may notice most cars use aluminum sealing washers on the drain plug, but those are typically against aluminum oil pans, etc. In any case, I use the copper washers against the cast iron risers, and they get replaced every 4 years, due more for distortion, not corrosion. Those pieces of copper are the least of my issues with the motors and corrosion. There is one more very important place i've seen Cu washers on these engines and that's on the bolt holding on the oil filter adapter. I've got one that's 30 years old, in the salt.."