On Jan 16, 3:56*pm, [email protected] wrote:
Is draining the block in an I/O enough to keep it from cracking, or could there
still be water pockets in it that could be enough to crack it? It seems they
should be designed so that can't happen, but are they? This particular one is a
140 hp straight four cylinder Mercury 1976-1979 model.

No, it is not.

When "winterizing", try hooking a shop Vac in reverse (if yours has
that option. My 29 dollar one does.) to the upper end of the rad hose
and blow air through the engines water passages while the petcocks are
open. It should get all the water out. Works for my V6 Buick. I have
those old " log " style manifolds.

Hook up may vary, but I hope you get the idea.