The factory manual is the ONLY way to go in my opinion. I have the factory manual for my XR6 and it covers just that motor plus the 250 and 200 2.5l EFI and thats it, they are all basically the same model. A chiltons you will get everything from 2hp to 300 and a lot less info. My manual is some 2 inches thick and covers 3 motors. The chiltons one i looked at beforei got mine was like an inch thick and covered like 30+. I would shop around on the price, also check on merc parts express. I pais like $26 for mine, its been worth every penny.