Welcome to iboats.
Does the Paint on the Head look like a little brownish? If so then it got pretty hot. Do a Compression Test. If the pressure are below 120, try a different Gauge. If still low, the engine likely has scored Cylinders/Pistons and would need to be torn down and examined. If the numbers are okay, then proceed as follows...
Drop the lower unit, inspect the Waterpump, and at the minimum, replace the impeller. That engine has an Overheat Horn inside the Control Box. You can verify the Horn and wires by ground the wire that goes to the Temp Sensor that is on the starboard side of the Water Jacket cover near the top of the Cylinder Head. When running use a Temp Gun to check the temp of the Top of the Cylinder Head and Engine Block, if it exceeds 150, then more troubleshooting will be needed