Re: service manuals
You hit the nail on the head...the factory manual is written for marine technicians who have or will acquire the tools they need, and have some basic level of training and experience, and will be working on their customer's motors instead of their own.
Seloc on the other hand, is written with the do-it-yourselfer in mind. It has some good general tips and special tool workarounds, and some good photography.
Unfortunately, those manuals cover so many different models, the pictures and diagrams might look nothing at all like your specific motor. I've known 'em to be wrong on a couple things, too. They don't know what kind of carbs are on my motor, for example.
On the other hand, in the OMC manual, the photographs and diagrams look exactly like my motor.
Forced to choose, I'd choose the factory manual.
Whatever you're working on right now, seloc is more useful to you but, hang on to that factory manual, you'll be glad you have it. Sooner rather than later, most likely.