Installed Sierra coil, metal core spark plug wires, and set points. Took her out for a test and she runs good at three-quarter throttle. Runs rough at idle. Not entirely sure of original problem but sure sounds like the old coil even though it tested good and the first cheaply built coil I bought that tested good too.
Sounds like carburetor issue now.
20hp is more than enough for my 16 footer.
Reverse engages when the motor is not running and clatters when the motor starts. I can start the motor and hold it in reverse gear OK. So, I have another thing to check out on a different thread.
My wife and I sure enjoyed the early morning test run on the lake. Very refreshing
Thank you everyone for your input. I learned a great deal.