Difference between 1997 & 1998 90hp 2 stroke outboard

[Rcuriston]

I’m trying to order a complete motor for my 90hp Mercury and ofcourse the vin tag is missing. I figure it’s either a 97 or 98 but when ordering a new motor they are different, 97 is by its self and 98-2010 are the same 2 stroke motor. Can anyone tell me the difference or a different way to figure out what year I have?

 

[jimmbo]

Welcome to iboats

The serial number should also be on a Disc(kind of looks like a frostplug) on the block.
The difference might be a completely different Powerhead, but it could instead be a different midsection, or transom bracket. Without Serial numbers, I can't even pick the proper parts lists, to compare

 

[markhodges78]

The welch plug should look something like this and located on top of the cylinder head