Re: OMC Select-Elec gear shift
there are two common types, the "Evinrude" type with 3 buttons for shifting and a throttle that only sweeps forward
The more modern style Sterndrive/Johnson type with a switch built in to the throttle that has a neutral in the middle and sweeps FWD and REV like most other boats
and then there are binnacle mount, side mount, concealed side mount, etc.
eBay if you want a bolt in replacement. Some repair parts are still available from an Evinrude dealer. Someone was repopping the internal switches in the Sterndrive/Johnson style and selling them on eBay.
the switches don't last as long as they could or should because there is no flashback diode in any of the systems used to stop the arc from the collapsing magnetic field every time you shift to neutral so the contacts arc and get burnt after a few thousand shifts.
and of course, any drum switch good for 10A or so can probably be used, but it will be isolated from the throttle - might even be one out there with diodes for arc suppression