I have a 502 gen 6 that I took to the machine shop and got back and suspect that it is not the same block that i brought in. I took the Merc serial number tag off the back before I took it in so I am wondering if the serial number on the Merc tag coinsides with the serial number that is stamped on the front of the motor. Thanks Eric

I don't believe there is a number stamped in the front of the block on a Merc engine.

the number should on the back of the engine behind distib. at least that is wear they are on car engines might be on side of block down by the exhaust also

Those are casting numbers. They won't be specific to any one block. Car/truck engines usually have a number actually stamped into the deck on the right front side. Not so in a marine application... thus the riveted on tag.

Some blocks I was trying to ID had a stamping on a small pad in the center on the front of the block behind the circ.pump. When I checked it with the merc tag it was the same...wasn't a gen VI though