My block casting number is 10051107. Everything I`ve found on the internet tells me that this is a Mark IV, 454, 4-bolt, Bowtie block with 4.25" bore siamese cylinders, but can be bored to 4.50".

My Mercruiser serial number is D622888. The customer service rep at Mercruiser tells me this is a 502 cubic inch engine.


My question is :
Did Merc bore block to 4.50 to make this a 502 ?

I`ve heard a couple rumors about Merc using Bowtie blocks to build the 502. Engine is an early 502 / carb.

What`s the story ?

Early 502's were Bowtie blocks.