On Jan 16, 2:32*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.

On my 140, U drain the petcocks, and pull the hose from the lower leg
to the manifold, and pour RV (pink stuff) anti-freeze down the hose
till it's running well out the lower end, and while leaving the
petcocks open on the manifold and the engine block, I pour the same
anti-freeze in the water pump hoses until it's running out all the
drain petcocks. I've had good success with doing that as well.

I've known of people who have taken the prop off the lower and put it
in a large vat (55 gal drum cut in half) , put the lower in it an run
the engine which gives the engine a total flush of water, but that
takes a lot of antifreeze and storing is a problem and it's a messy
set up.... but it works.