Help with an old serial number

I have found the number plate under the hood of my motor. This is not as helpful as I had hoped. The numbers I have found seem not to be leading to a proper Id of my engine and exactly what parts I need to do a repair.
The plate shows: Model #10573 then Serial # 2418 Am I correct in thinking that this means the engine was built in 1973, and was the 2418th engine of this power rating built When I try to look this serial number up I see a set of numbers followed by a pair of letters.
Is there somewhere on this motor that I can find more identification numbers or some specific information leading me to the actual year of manufacture of this unit? and what manual I will need to identify its parts.
The boat is a 1969 Chrysler 16 foot and I am sure this is not the original motor as the boat is rated for 90 HP on the tag and it has this older 105 HP installed. Any help and suggestions would be appreciated, I have worked on auto's but I have never tried to rebuild a boat motor and I would like to have a chance to not turn this into a spare anchor..LOL.
Larry

Prob 1969..
There should be a foundry stamp on the side where the fuel pump is located.
It should be close to the top.
Or under the bottom carb on the intake manifold, there might be one there.
The stamp is usually about the size of a quarter, the center has a number that should be the year.