On Merc motors, is there a Stamped series of numbers on the block itself that would tell me about that moror? such as if it's a 500 hp or a 502? No i'm not talking about a tag, I'm talking about a stamped series of numbers right into the block like general motors has.

There should be serial number on the block if its a Merc motor that any authorized Merc dealer should be able to punch up in Mercury's system and give you the history on. Thats how they know when you are out of warranty when you go in for service. I know my 502mag has the number on the valve cover and on the back on the block, I dont remember if it was on the head on the actual block but I remember seeing it somewhere.

Ok thanks. I wanted to know. I was reading another thread where a guy painted motors blue and they had No tags at all. Turns out they weren't true blue motors . So I thought it should at least have the stamped numbers on the block somewhere if all the tags are removed

MK IV blocks (and GM small blocks) have a GM production (RPO) # stamped on the cylinder head gasket surface at the front of the block. Gen 5 may have them in the same place. I believe the Gen 6 # is stamped right above the timing cover. The number was coded to provide info as to vehicle model, engine model, and transmission type. Newer (early 70's?+) also had the VIN included. Engines destined for GM parts counters, warranty replacements, other OEM's, etc, had a different code stamped in. Mercury Marine added a serial # tag to the back of the block, and also some models had a sticker on the valve cover with the same serial # stamped in. Gimbal housings and outdrives also came with similar serial # stickers on them.

This may help some. A complete listing of GM casting numbers. Although not marine specific, it will tell you what year engine/ head it is.
http://www.mortec.com/bbc.htm