I got myself a small Turnigy Centurion, an ARTR fast electric catamaran around 45cm long (18").
Just have to add your own receiver and batteries. Motor, ESC, steering servo are all factory installed.
Build quality is overall quite decent. Hull as survived a few crashes (blowing over) without any damage. Hull is gel-coated in black with stickers. Canopy is also fiber glass.
Hardware is half plastic, half metal: strut and turnfin hinges are plastic; turnfins are stainless seel; rudder is alloy (and features a water pick-up).
Motor and ESC are water-cooled. Not much info on the ESC. Mine came with an XT-60 connector already soldered (and an XT-60 female one to solder on a battery). No information on whether ESC can be programmed.
Low-voltage cutoff is set a little low for my taste (looks like 9.9V). I now run it with an external low-voltage Lipo alarm which monitors each cell individually. When either cell reaches 3.3V unit starts beeping (loudly). Additional weight is negligible. I suggest some WD-40 or maybe some varnish be applied to the PCB to make it splash proof.
Which brings us to another topic: there's some water ingress. I still haven't found out where/how water gets in. Water cooling circuit seems watertight: with pressure applied with a syringe, no obvious leaks.
The complex canopy shape makes it tedious to apply tape (I use 3M Blenderm) and I suspect water gets through around the canopy. I ended up with a few drops of water on the low voltage alarm PCB which triggerd the alarm on one cell. Cell was actually still at 3.7V.
I decided to go with Turnigy Nanotech 3S 2200mah 25-50C batteries.
They end-up warm, maybe 35-40°C or less. Might have gotten cheaper ones but they aren't very expensive altogether so ... They came with XT-60 connectors so no soldering. Yay!
As listed above I changed the stock prop (which was actually broken after hitting a floating tree branch) for a new 32mm (pitch 1.4) CNC machined aluminium one.
The CNC aluminium prop is "longer": I had to move the drive dog far forward to be able to put the locking nut back on the shaft. And it fits barely. I should probably grind/extend the notch on the shaft to move the drive dog even further forward. But so far it works.
Don't feel I gained any speed but boat feels a little more stable. I might have to raise the prop-shaft a little to get the prop (which is 2mm bigger) closer to the surface but there isn't much adjustment range. ESC, motor and battery aren't any warmer with the new prop compared to the 30mm plastic one that came with the boat.