If you cut the rated duty cycle of a 12v winch down to 1/4 of its rating when using it on 24v, it will be fine. Ohm's law, V = I x R. R is fixed, and we are doubling V (voltage), so I (current) also doubles. W (watts) = I x V, so if it was initially a 3000W electric motor, it is now pulling 12,000W.
Very short duty cycles are OK, but the motor will heat much faster, the brushes/commutator melt (hottest part of the motor), the insulation melts off the wires, and it shorts out with a burning smell we all know. She'll do it, but she will get hot, and very quickly once under load. Splashing water on the motor case does not do very much to alleviate this. It will do it, but for how long is a gamble.
If you guys have ever used a hydraulic one, you would not want anything else. They can be had cheap, and run off the steering pump. MileMarker makes them, and they can be had for peanuts, used. Mount it on a small hitch plate, and have a receiver in front and rear of the truck, with some Bobcat type quick connect fittings on the steering pump hose. Their ability to work under water and 100% duty cycle is fabulous, plus they are impervious to rain and weather exposure, unlike an electric one.
If you have a 12v, just run it on 12v, the duty cycle is short enough already at that.