Based on the Cowl and Faceplate Decals, I'm almost 100% certain it is a 73
A 73 has Mercury Marine on the Face Plate, a 72 would have Kiekhaefer Mercury
In 74 the two blue stripes would have not gone under the Face Plate.
Granted, this is my 1984 115, kinda looks like a 71, cause I put the 71...