Engine Identification ?

[redxpuser]

Can anyone help with POSITIVE Identification of my Outboard Engine ?

All I Know :

MERCURY
200
Thunderbolt Ignition

Serial Number : 9018324

Can't seem to find a site with the answer.

[Nos4r2]

It's a 20hp Mercury 200 made somewere from 1973 to 1983ish. I'd err towards '73 to '79 looking at the pics under the cowl. The serial number doesn't match anything on the oldmercs.com site.
Got a pic of the cowling? The year may be identifiable by the graphics.

[redxpuser]

Cheers NOS, I'll just go and take a picture, back in a minute

[redxpuser]

Here's the picture

[Nos4r2]

It's an early one from the cowling-It looks remarkably similar to the 1973 one I had.