Sounds like you are in a very good place. You are able to help a friend who is giving you a great price, and you know the entire history of the engine and the maintenance it has received. It really doesnt get much better than that. 600 hours is not alot of hours considering the year of the engine, especially if it has been well cared for. On the other hand, 600 hours is a whole lot of hours if the engine was not broken in correctly or maintained appropriately. I would probably buy the boat if I was in the market for a used boat and enjoy it for a year or two. Keep your gas fresh, run good oil, and have the engine checked out by a good mechanic. Merry Christmas and Happy New Year!!!