A reliable motor might increase the value, but sadly, you almost for sure wouldn't break even on a new motor come resale time. Old 2-stroke outboards will run for a long, long time if they don't sit with the carburetors full of
fuel, but most of them have. It evaporates and turns into insoluble gunk.
whether you'd get your money back or not, you need a motor for security. I would recommend a new 2 stroke. They are
fuel injected, which makes them
fuel efficient, non polluting, light for their power... if it wasn't for how bad the old ones stunk, polluted, and wasted
fuel, modern ones would be very popular.
I don't sell or represent any boat motor products.