Yes the MFJ-925 tuner will work
. Obviously it has to be in a dry, protected location. If you can make it so at the feedpoint of your antenna
and run coax and power/control cable from the transceiver to the tuner in that position, that would be ideal. If not, and the tuner has to be close to the transmitter, I would run low loss coax like LMR-400 or RG-213 from the tuner to the feedpoint of the antenna
where you would attach the center conductor to the antenna and the shield to your ground/counterpoise. There will be some SWR related power loss in that cable run, maybe as much as half of your power at higher frequencies, but it will "work".
MFJ has a reputation for automatic tuners that work well, but they also have a reputation for sometimes sloppy assembly. I have never had problems with their products. They also sell some weather
protected/sealed tuners designed to be placed in less than ideal locations. Cost a bit more, but less than an AT-140. They can be powered via coax using a bias-T connector to minimize the amount of cable running to them. That would be a better solution, but a bit more money