I purchased both the Clymers and the Seloc OMC Stern Drive manuals. I found both to be highly informative and helpful in taking care of my OMC engine and stern drive. If you want to completely overhaul the engine and/or stern drive, get the Clymers. The Seloc will show you how to overhaul your engine, too, but, if you want do routine maintenance on the entire boat; such as the steering, shift boxes, tilt, propeller, engine and stern drives, get the Seloc. The pictures are a little clearer and more crisp with the Clymers, but the Seloc is my pick for the most useful information. I have no intention of pulling the engine and tearing it down to the main bearings which the Clymers does an excellent job of explaining. I did want to know how to pull the exhaust manifolds and a general diagram of the workings of the engine and stern drive. The Seloc does it for me. It is about a fourth of an inch thicker than the Clymers and has all the specification in the back. Clymers has specifications dispursed throughout the book. The Seloc (which is Coles spelled backwards)does a good job of separating the differences in parts and procedures between the pre-1978 models and the post-1978 models. (Personally, I feel there is enough differences between the two to warrant a separate manual for each.) If you've got an older boat with an OMC Stern Drive, the Seloc manual will be a big help keeping it running at top speed.