Fire guns are a popular special function on fire boats, tugs and supply vessels. To switch the water pump, a simple RC switch or a switching channel of a multiswitch decoder is sufficient; depending on the current consumption of the pump, a relay must also be used.
If you want to hit a target with the extinguishing guns, this is not so easy, besides the use of all manoeuvring functions, a regulation of the range of the water jet is very helpful. If you give it a proportional channel (ideally a linear slide), this is achieved with a simple speed controller, as used for controlling propulsion motors.
Of course, the used controller doesn't need a complex polarity reversal feature, which is why the other controllers presented on this site are out of the question. In addition a minimum range should be adjustable, so that the own deck is not flooded when operating the extinguishing cannons. Also a controller with very sensitive behavior at low throttle, as desired for propulsion control, is rather unsuitable.
The pump control module presented here is a speed controller without polarity reversal. In addition, there is the possibility of setting a minimum speed. The reduced value range between the minimum speed and the full power is linearly mapped over the entire stick travel, resulting in a very well adjustable range beyond the minimum power.