Hi Steve,
Somewhere on the forum here is a previous discussion of this issue. Jim Shaffer found the King County laws, and has them linked in that thread. I'm too lazy to find that thread, but may look after I type this.
After reading through those laws, it was clear that King County DOES NOT SAY you CANNOT have an internal combustion engine attached to the back of your boat for "No internal combustion engine" posted lakes. Go ahead and launch your boat on the lakes you listed.
The WDFW laws are like you said, only applied to lakes in the special rules section. The purpose of these is usually to give folks looking for a canoe/float tube-type experience a lake free of heavy boat traffic. Hence, there's only a few in there with this regulation. In fact, it's pretty dang rare when you consider how many small lakes are in our state.
To make a long post longer, the problem is that local homeowners don't understand the difference between state and county regulations. And you can end up getting hassled. To make it even worse, sometimes even law enforcement gets the regulations confused! I will continue to fish lakes with a IC engine-equipped boat (dang - need a boat) and would heartily challenge any ticket given to me by an officer. I have only heard of one occassion where someone was ticketed, and that was on Steele Lake. No bass in there anyways!
State reg = don't fish with IC equipment
King County reg = go ahead.
I haven't tried to figure out the other counties yet...
Clear as mud,
Chris