Stmjxxi
All done and working. Thanks for the great advice.

The switch had 3 wires - see photo 1. I replaced it with the centre-off switch and turned the switch so it is orientated sideways. I did a bit of multimeter testing before I swapped the switches. With this arrangement the servo works very well. Left - off - Right. Perfect.

Photo 2 shows the front of the Transmitter with Ch.6 (previously modified as a throttle).

Photo 3 shows the circuit board where the Ch.5 wiring from the switch is connected.

I have also modified the switch on Ch.7 and put in a joining bar to use both Ch.6 & Ch.7 together. I have seen this arrangement on real boats so it is realistic. The joining bar can be removed if required. Photo 4. The Ch.5 switch is on the top right of the transmitter.

I put all the radio components back in the boat and they work well in conjunction with the motors operating. No cut-outs.

Thanks again.