The 150 XR2 Motor is a great motor. I had one for several years before upgrading to a 200 Merc. They run real well and mine was trouble free. In a worst case scenario.....meaning that you need to re-sleeve a few cylinders, replace crank, rods, bearings, pitsons, reeds, etc. and rebuild the carbs, I would think you may be looking at somewhere between $2,000 and $2,500. If the boat is in nice condition, I believe it is worth it. Good Luck!