You can use that 240v outlet, but I don't think it is a good idea to put a
small tool on what is probably a 40a breaker. I would replace the breaker
with a 15 or 20a and replace the outlet with an appropriate outlet. That
the wire is too big is good.

Motors drawing over 15a @ 120v should be wired to 240v. They will draw half
the amperage, so voltage drop is smaller, especially with starting. It is
not really an issue with your jointer, which is probably only 10a UNLESS you
will also be running your dust collector on the same circuit. Then you
should rewire one to 240v just to get them on separate circuits. Are you
following me, or am I too tired to be coherent? You basically want to avoid
running two tools on the same circuit (at the same time of course). If
rewiring will prevent that, then rewire.