How to determine the serial number

[bobbutts]

Brought a very used boat and motor. Need to order some parts for the 9.8 hp 110 mercury, but the first couple digits of the s/n are scratched out. Last 5 digits are 80504. I'm guessing it's a 1968 to 1972 motor. Any other way to tell the s/n than the plate below the front of the motor? Thanks!
Bob

[ltjerry1]

unknown serial number

clean the plate with a rag wet with bleach. get a piece of white paper and a no2 pencil and run the pencil back and forth over the paper on the plate and the numbers should show through hope this works jerry

[boatmangc]

There should be a "freeze plug" on the block with the serial number stamped in it.