The only time Ive been in that situation is because the shift lever has already been broken, so I dont care what happens to either because I expect to replace both. Whats even more fun is when the shift lever is frozen in the orifice. That usually result in drilling out the nub of the lever too.
If you need to hold it in place Ive had success using long reach vice grips to steady things for drilling.
On at least 80% of the 6hps I deal with, the shift lever is broken. That little screw is stuck almost 100% of the time regardless of salt or freshwater use. For me its been really just random luck to get things loose.
If I try to remove them they generally twist off. Then its about using a center punch and drilling a good pilot hole using a very small drill and using some care/experience to try and make it as centered as possible to get things lined up. I use a hand drill. Yes, a hand drill and a steady hand works with the right level of focus.
Just want to point out that from my experience, its a 50/50 shot with these situations that these little 6hp motors will probably have rod knock or several other maintence issues to go aling with shifter replacement. (i.e. Gearcase, carburetor, oddball, etc.)
#laboroflove
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