This machine was built by Merryweather's of London, a prolific manufacturer of fire-fighting machines, in 1836. This would have been operated by at least seven men, one, at least, to aim the hose at the fire and the other six (three on either side) to pump out the water.
Personally, I can see it has 'GWR Kingswear' painted on the side but I can only guess that it was used at Kingswear station, where this photo was taken, as a fire pump in the later part of its career.