86 Evinrude timing setup

[chrisire]

Is there a proper way to set the timing on my 1986 Evinrude 20 hp outboard without having it in the water at WOT? I would rather not take it to a specialty shop and pay them to do it. There has to be an accurate way the average joe can do it themselves.

[boats.net]

You can disconnect the linkage to carb in order to advance timer base without advancing carb throttle plates but it's not 100% accurate as actually running.