where do I look for serial numbers on twin small blocks? Not much room in there!

are they mercs, if so, they would be on the block stbd side at the back of the engine by the bell housing. There is a metal plate attached with the #s on it

What kind? ie: Merc?

Do you mean casting number or manufacturer serial number?

There's gonna be a casting number molded on the block, and lots of serial numbers are on the transom assy, and on a small plate riveted to the block. Not far from the starter.

yeah mercs, thanks
looking for manufacturer serial number

If they are original, I would expect a little red aluminum plate (like 1.25 inches by 2.0 inches) pressed into rivets on the block, next to the bellhousing and not far from the business end of the starters.
Should be duplicated on the transom assy bracket also, very near where the steering arm passes.

thanks