I bought a 1979 25hhp Johnson that had overheated to the point the
white paint on the power head turned gray.
Compression was 90 in both cylinders, complete new water pump, so I bought it.
5 years later, it still has 90 compression and runs good.
Second motor: 1988 35hp Chrysler Force.
Seller said it overheated to the point that the warning buzzer sounded.
He said he rebuilt the water pump - so I bought it. (after having good success with the Johnson)
Problem was not the water pump - it was the thermostat .....
He probably did 90% damaged to the motor.....
The remainder 10% was on my watch.
The motor is toast - 60 compression on top cylinder, zero (0) on the bottom.
So make SURE you know WHY the motor overheated...... it could be a couple of reasons.
If it has good compression, I would say use it . . .. just keep an eye on it until you are comfortable.
If it were mine, I would add a little more oil to the gas for a little more lubrication until
any glazed surfaces get back to normal.
Jus my dos centavos