At the beginning of this season I had a leak in my return line also which I replaced. Mack Boring did have the part for my 3YM30 and they are great. Don't know if your engine is similar to mine but a couple of hints that were told to me. Be sure to order the metal washers that fit under the return piece on each cylinder as they should not be reused. Do all removal and retightening using 'reciprocal wrenches; that means use two wrenches on each joint so nothing else comes loose. Check that the plug is tight in the engine before putting the return line back on. Use 12 sided-closed end box wrenches for all joints and torque each. That's it. All worked fine.