>>1090604Marine deep-cycle batteries are good for about 50% of the stated amp-hour rating of the battery.
So if that battery's rated at 100 amp-hours, multiply by 0.50, resulting in 50 useable amp-hours.
If that motor's drawing 10 amps, that battery will drive it for about 5 hours.
Automotive starting batteries are usually only about 20% amp-hours, since the plates are designed to provide high current for very short periods of time.
Don't have any related images on this computer, so
>pic unrelated. 
