1976 20 hp Merc, where is serial number

[fiddlinman]

I notice a number on back of motor transom mount and one in front under motor. But when I try to order parts the site tells me the serial is a different number. Can anyone tell me where it is?
Thanks

[Ski]

There should be a tag on the transom clamp just under the front of the motor. It's usually covered with grease.

[h2osprayer]

I have the same problem. spent a half hour on the phone with mercury and they said it is probably Canadian. Never got any solid answers so stuck without seals for a 20 hp model 200.