Then that is going to be difficult to pinpoint the year, looks like a late 60's to early 70's model, depending on where you are located, you should be able to get the state to issue a new ID number for it, then you will have to put it on the boat.
I would contact the agency in charge of issuing boat titles, registrations and see what they recommend, they can't do a background on the boat if it has no numbers so see what their procedure is to getting it back to being able to use it. It is a good looking boat worth saving. I am not familiar with Canadian laws at all, so get a hold of them.
In many cases the boat and motor were bought at the same time, take the ID number off the motor and track the year down,pretty sure the blue band Mercs were early 70's.