So I bought a rebuilt 140 block...now I have a few questions.

[tcooke]

It is a 1978 Mercruiser 140. The block has been completely rebuilt, new pistons, bearings etc...

First, which serial number do I go by? the one on the block or the one on the valve cover? As they are different.

There is a large metal flake in the blocks cooling, how should I get it out? And will small flakes matter? will they get chewed and spit out?

The head, manifold and exhaust pipe are off to the machine shop to be tended to, if I am not mistaken they can give it an acid type bath that cleans and gets rid of any rust.

Any other tips for a first time Marine rebuild?

 

[JustJason]

Re: So I bought a rebuilt 140 block...now I have a few questions.

Impossible to say without seeing the block and how bad the scaling is. That's 1 of the tricky things about rebuilding used marine blocks... the cooling system.
If you had a machine shop do the work/measuring/piston fitting etc you should have had them dip the block.