Finding out if 8.1 Engine is HO or Base?

[mckaras]

I ran my engine serial number through the database to find out which 8.1 it is on Mercurys website and it pulls up 4 engines which 2 are in my serial number range... Is there anyway to tell if it's an HO or Base by looking at it?

Serial number - 0m318790

 

[muc]

It was built 09/26/2003 By MerCruiser as a base engine and installed shortly later in a 1986/7 St.Tropez

If I remember back then the cam and throttle body were bigger, and different software in the PCM,