Hi Martin,
It is very unusual for the motor to get hot under normal conditions as it has a built-in cooling fan. Likewise the ESC which has heat displacement case.
I would suggest that you look elsewhere for the problem, it could be in the prop shaft perhaps being tight in the tube/bearing caused by a small amount of bend in the tube when fitted. It could perhaps be the size and type of the propeller ie is it a fast electric propeller? Is the fuse fitted between the ESC and the motor or is it between the battery and the ESC.
For the motor to get hot a resistance between the motor shaft through the shaft to the propeller tends to be always the main reason. If the motor is dragging then the ESC will get hot and eventually blow the fuse as the resistance is increasing the current pull on the motor and the ESC and the fuse. If this is the case you can insert a 20 amp fuse..
If the fuse blows straight away it will mean that there is a short in the line anywhere between the motor and the battery. Check the wiring for heat if this happens as it could ignite the wiring.
Best Regards
Graham
I have recently completed a Fairey Swordsman following Bluebirds very helpful Plan for Beginners article. I have fitted a Hunter Systems RS540-SF motor controlled by a Mtroniks Viper Marine 20 ESC protected by a 15 amp fuse running a bog standard 35 mm 2 bladed prop. The Swordsman sails beautifully with a good turn of speed, however, after five or ten minutes running the fuse blows. Is it normal for this type of set up draw in excess of 15amps or have I got something wrong?
Martin Bright