4 bolt main caps truss the webbing in the block and reduce flexing under
extreme torque and rapid RPM changes, as in bracket racing. Little
positive effects in a marine type operating environment.
JR

bob wrote:
I may be replacing the 5.7L Mercruiser (Chevy) so am trying to get ahead and
ask some questions early. I understand that a 4 bolt block is stronger, but if
you build a 300hp (or less) motor, will it really make any difference? At what
point do you see a 2 bolt block breaking (what HP)? Will a 2 bolt go up to
350hp and hold up? If I indeed need to replace the motor, I plan to look for
an automotive short block and install a marine cam, use all of the mercruiser
other parts (manifolds, distributor, starter, alternator, etc.) so I should
pretty much have a "marine" engine but not at the prices Mercruiser wants.

Thanks,
bobby
bbusselman at hotmail dot com