On Fri, 09 Dec 2016 17:14:01 +0000, charliesal7
m wrote:

replying to John G, charliesal7 wrote:
It is a 10 guage wire. If i connected the wire to a 240v switch in the house
could i replace the box on the garage without having to put in a thicker wire?

If the wire coming in is really 10 ga (it really does not look like
it) and you do not need a neutral in the sauna, it could work.
As was posted above, it is better to put in a breaker style
disconnect.
Reidentify the white wire to red on both ends, connect them to the
line side of the breaker, connect the wires to a 2 pole breaker in the
main panel.
You will have 240v but no 120v loads can be served.