Identify Mercruiser Chev engine

I have acquired a chev mercruiser SB engine. Need to know which model and how much HPower it has.

I found a service manual for 1978-84 models and it shows a distinctive shape stamped into each end of the heads to signify hp. It also shows a Mercury number stamped into the block.

I cant find the number stamped into the block, and the shape stamped into each end of the heads is a block letter " L " laying anticlockwise on its back. This is not same as my book so must be different year.

Looking for help with identifying motor please.

 

Without knowing if the engine is OEM and never been rebuilt it's a little tough.
If you can get me the actual block casting number as well as the head casting numbers I can at least decipher a little for you.

Being that you have ab early book, could you check my latest post "OMC /SBC Question" maybe your book will have the information I need.

Thanks Gary

 

should be no Mercury # stamped into the blok, but there should be a tag on the side of the block where the flywheel housing meets the block