Originally Posted by gfackrell
333882 casting number
This is a low compression emissions head found on 350s and 400s. The piston it's covering will do a lot to set the complete compression ratio with a circular dish which can cover a range of sizes from 10 to 20 something CCs.
Compression needs to walk with the camshaft this gets into the subject of Dynamic Compression Ratio (DCR) which is a measure of stroke lost up to the point of intake valve closure. Under any circumstance low compression costs power while increasing fuel consumption but especially when combined with any amount of aggressive cam (say over 200 degrees of duration measured at .050 inch lift it really cripples engine power and increases fuel consumption.
For a boat I'd really recommend an aftermarket head, these come with a lot more physical beef which takes the punishment that running with high loadings for long periods of time that a boat requires. From that you taylor the chamber size for the needed compression ratio.