If you angle it in a rearward direction underwater to create a little reduction in pressure at the exit or put it just behind the propeller you can force flow through the cooling pipe at a greater rate. I once did that with a boat and had the inlet facing forwards and the outlet behind the prop without even bothering with a pump.
There are many however who would also suggest that, if you get the motor, battery and propeller correct, that you shouldn’t require cooling, unless it is a very high power set up. As usual you cannot beat experimentation and buying yourself an infra-red temperature sensor is a worthwhile investment for such a trial. Hammer it around the pond a few times under deferring conditions and immediately take a reading of the motor casing. Let it cool back to ambient and then try a different set up. You may even surprise yourself!
Edited By Richard Simpson on 28/02/2021 11:25:03