The 3.0 liter Opti's have had some issues since being introduced around 1998. Over the years, Merc has addressed a lot of them. If I were looking at a rig with that engine (or any used engine), I would find a good tech and have them go over it with a fine-toothed comb. If need one, the folks at Bunch Marine in Harriman run a very good shop and know the Opti's well. Opti engines are very good on gas and oil especially when run in the 4-5K RPM range. Get on BBC and read the FAQ's on the Merc boards. Pay special attention to the recommendations regarding maintenance, oil, fuel/fuel additives, battery, and operating temp. VERY important to let these engine warm up before dropping the hammer. On a 22' Ranger, I'm thinking you'll be lucky to crack 60. Have a good one!