Have you checked the oil quantity AND quality in your drive?
You can drain the gearbox by removing the lower drain plug and the filler plug on the drive.
It's possibily full of water and your drive just seize when hot...
yes servicewater pump checked over was it stored off the boat if attached to an aluminum hull (electrolysis ) check over for corrosion internal and all wiring connections in any water jackets or intakes ..mud wasp nestsor rodents
There should be two hot wires one from the battery and one from the switch the one from the switch check should be hot when the key is held on the start if it is the starter solenoid is bad