One quick and dirty test to see if it is locked up is to remove the spark plugs. And see using a plumber wrench or something similar to see if the crank shaft even turns. That's a good sign.
A 14 footer with that much power (155 hp) sounds a bit UNUSUALLY HIGH. Maybe a 24 footer?
The carbs are full of crap, so new fuel probably won't do much good. Maybe breathing ether into it will for a few seconds?
Probably engine belts are dried and ready to break too.
As far as the hull, see if it has been retaining water. The inside will have a jungle of mold if the water was sitting inside.
See if deck is spongy. No spring.
Dry rotted tires are normal for it sitting in sun.
Is the rpice right to see if its worth spending some $. Changing the oil is the least of your worries. In fact the old crankcase oil may be the best feature left on that boat.
