The block should not be damaged at all. Those engines are tough and I have seen one run so hot it melted the exhaust hoses and ate the flaps off of the impeller. As far as I know that boat is still running great today, three years later.

I would find out what is causing the problem before I buy the boat, possibly just an impeller or clogged line. If the deal is sweet I would buy regardless as long as the problem of overeating is fixed.

If it is a good deal, shoot me the number for it and I might buy it.