Due to rubbish weather at the moment delaying the launching, I thought I'd fit fans to the ESCs, as I noticed them getting slightly warm during testing. Fans (5v) now come on with the cooling pump through a 5v UBEC, and powered by the same 2s 1800Ma LiPo as the pump.
Also made a few brass tube fittings to divert some of the cooling water to some new side outlets (vintage 'Frog' fittings from my collection). Another small refinement was to fit mahogany anchor chain/ warp rubbers at the forward fairleads.
Have also fitted a battery monitor/alarm which is visible for checking through the rear cabin window. If it keeps raining and the wind keeps up I might think of something else to do to it. It's already a plumber and electricians nightmare! (I want smoke but I've run out of room! (I'm working on that though.

Finally got a reasonable day and got the model on the water for the first trial, - goes pretty well (see vid) A few small trim tweaks and she'll be set. Very economical on the batteries as well.

Not much to add really, just made a drip tray on the back of the stand for the prop shafts. They are ball bearing shafts and weep quite a bit of oil, (a good thing as it cleans out any water)

Had a small issue with the water pump speed, as on 2s it was a little slow. A 3s was a bit much for the motor to run flat out at max voltage (even though it's a 6-12v motor) and I really wanted something around 10v so as not to wear the pump diaphragm out too quickly. I also wanted a better flow of water from the side outlets and exhaust.
I had recently purchased a couple of cheap voltage controllers from Ali Express, which work well, so I fitted one in the power line to the pump and ESC fans (fans are limited by a UBEC) and it's now adjustable to suit the flow required.

I was thinking of fitting a small 10A ESC to match the flow with the throttle but it requires a lot more wiring, this was just a 10 min job. Next job is to throw the boat back in the water and set the flow.

Just fitted this IC 3 way fuel tap, for balancing the water flow between the rear exhausts and side tell-tales. Too much was going to the exhausts, as the tubing is a larger ID. Works well with the new voltage controller to get the flow just right.

Re Dougs' comment and recommendation re the Hobbywing ESCs (and the better fwd/rev capabilities) I decided to take a punt and buy a couple to try. Fitted them with a bit of re-wiring and they work very well. The cheapo ones I was using (with fans) were fine but had the jog forward to reverse feature (safety feature for rock crawlers) which was a mild annoyance. Not sure if $18 as against $50 for 2 ESCs is really worth it just for the convenience, but it's done and working.😊 (it's only money, right?)😐 Tanks Doug!😁😊

Also I swapped the sound unit in the MTB for the newer self contained one in the ST, so the ST now has 2 the same and I don't need the extra REC any more (due to the incompatibility between the 2 types ) Another lot of re wiring, but it's much better now and all happiness filled😊. Just have to buy the later speaker which is much better, (can actually have 2 speakers on each unit, plus sirens, lights, indicators etc) (only another 20+ wires to fit)
JB

With Grahams' help with the circuit diagram and suggestion, I've managed to make a switch for the smoke in the ST, which is operated by using the spare rudder channel on the TX. Moving the stick left switches on the smoke and air pump and right switches it off. I used two 5A micro switches, a 3A relay and a micro servo to make the switch. Works really well as I had run out of switches for the smoke and air, (already have lights and water pump on the available switches) and only had this option left.

Pics are of the test set-up and the switch installed in the boat (center of pic). Also shows the air pump and 'pen' type smoker in place. Have 2 small voltage regulators in the stern for the different pump and coil voltages (one in place). Also shows the new plumbing for smoke, water, air.
JB