Are you near the boat? As stated previously, everything depends on how well everything was maintained. Go over the boat, look for things that are easier to maintain. Oil levels, strainer condition, belt tension & condition, etc. If easily maintained items weren't, you can bet harder, more important things weren't either. if the engine has a heat exchanger, then the time in salt water should not be an issue. (Check Anode(s). Fresh needs magnesium and salt needs zinc.} Ask to see a maintenance log. It doesn't have to be fancy, for example I just keep a list on my laptop of what has been done and when.