Older boats like that sometimes had raw water cooling, inlet thru hull fitting to pump to engine, some had keel cooler, a pipe running next to the keel, or a heat exchanger and pumps .
Pix will help .
There is often a way to rig cooling to garden hose, imagination may be required. Find a pump inlet and rig it to a garden hose, (turn it on) lol, watch for leaks . Water has to go somewhere, (exhaust manifold), don't fill the boat .
Water cooled Marine exhaust manifolds often leak coolant into the cyls, so scrutinize spark plugs for residue/salt .
Make sure all belt driven pulleys/pumps turn when running .