If the boat and motor have been undercover most if not all that time, and that's a real nice boat, and the motor might be mid 80s model?
Give it a run, if it's done stuff all hours, as people have said above , get it turned over by hand and give it a start. Good chance it will run, be it rough, and pump water. If it does, leave it run for 15-20 mins . Change the gearbox oil and take it for a 15 min water test on the river. The motor is more than likely going to be ok. If it runs reasonable, then get all the bottom end seals and water pump replace for good measure. If compression is good,