I think
THIS is still the same Cobia Manufacturer. There's also some stuff
HERE. '67 won't have a HIN (probably) but maybe Cobia can help you via the serial number on the capacity plate (assuming it still has one).
I have no clue as to what your registration laws are in Texas - the local constabulary is the gang to ask. Here in TN, you don't title boat motor or trailer ... but if you don't register the boat you'll have a heap o' trouble on the water.
If you raise the bow of the boat way up, and remove the plug (hopefully it's out already) how much water do you get runnin' out?