On the boat the anodes still on a closed system with coolant salt water cools the coolant thru a cooler Or on my boat I have Keel pipes attached to the hull Ocean water cools the engine coolant inside the pipes zinc anodes attached to the pipes as sacrifice to the sea

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commercial fisherman diesel in my blood in my boats trucks and Dear old Dad has had me drivin them since i got my first license in 1968
1986 300 SDL 427654
1999 Chevy Crew Cab Dually 225423
1986 300 SDL 287000 Dad's
1987 190 Turbo 158000 Mom's (my inheritance)