Make SURE that motor had a LOW pitch prop on it ... as if it didn't, I wouldn't buy the engine. Reasoning - a low pitch prop is needed to push a big load. If they kept a normal pitch prop on that OB, then I'd guess that the OB was seriously lugging ... and that really puts a tremendous load on the OB and its longevity. Less not adding oil, lugging or wrong prop use, is about the fastest way to kill a motor ...
On any decent skiff, I'd bet that OB would typically run a 15 to 17, if not to 17 to 19 inch pitched prop for speed use. Therefore I would expect to see a low, 'big eared' 11 to 13" pitch prop on that OB - maybe even a 4-blade prop - if truly configured to push along a big, heavy pontoon boat.
If not ... I myself wouldn't chance it ...