High hp and OB concerns

[Arminius]

Newer gas engines: outboard, I/O, & inboard, produce more hp per cu. in. than the leaded gas supercars of the 60's. My truck's (XT5) 1.4 hp per cube is achieved through a compression ratio of 11.5:1. These new aluminum heads avoid knock through careful immediate (reverse flow) cooling of carefully designed passageways in the heads with pressurized coolant that does not boil until 265 F. The design problem was avoiding vaporization which would defeat heat transfer, resulting in destructive knock. I am unsure where marine engines stand but this output level could be achieved with fresh water cooling. But what do these big 4-stroke outboards do? Those passageways would deteriorate quickly on raw water. Maybe they have heat exchangers too. I pine for the 2-strokes of yore.