Re: 73 evinrude 135
You have to disconnect the shift linkage located under the carb. There are different types, I have a 1974 Johnson 135 and on it the shift linkage comes up under the carb. To dissconnect it you follow the 2 flat shift rods back to the linkage side of the motor, there you will find a 5/8 bolt that goes threw both plates, loosen this bolt (you might have to loosen the small nut at the linkage as well) loosen the 5/8 bolt until the 2 plates seperate about 1/2" then reach in with a flat screwdriver and pry them apart and that will pull the pin out of the top of the lower end shift linkage and allow you to drop the bottom end.
Note*** before you start this ...replace at least one of the bolts that hold the bottom end on so that it will not fall off when you disconnect the linkage.
I hope this helps...if you need more just ask.