I’m building a USV based on a ~2.5 m inflatable monohull boat (full-load displacement 200-250 kg), with ArduPilot autopilot and skid-steering propulsion (differential thrust, no rudder). Target cruise speed is ~4 m/s. I’m planning to use a pair of T500 thrusters and I’d love some real-world feedback before committing.
**My main concerns:**
**Propeller diameter & efficiency at surface** — Compared to a trolling motor, the T500 runs a much smaller prop at much higher RPM. For a displacement hull at this speed, is that a meaningful efficiency penalty in practice? Also, any known issues with air ingestion or cavitation when running close to the waterline?
**Slide steering authority** — The two thrusters will be 100 cm apart (centerline to centerline). Is that sufficient for responsive differential steering on a 2.5 m hull at low speed?
**Upgrade path** — The T500 is the most powerful option in the Blue Robotics lineup, so there’s no room to scale up within the ecosystem. As an alternative I’m considering two trolling motors (40–50 lbs thrust each), which would offer a much wider upgrade range. My preference for the T500 is mainly the native ArduPilot integration, though I know trolling motors can be adapted too.
Has anyone run T500s on a similar configuration? Any experience or suggestions are very welcome!
Hi @madro -
Welcome to the forums!
I don’t think you’re going to achieve anywhere near 4 m/s with T500s - but not because the thrusters don’t have enough power. Differential steering won’t be a problem, especially as ArduRover will reverse the motors - you’ll be able to pivot turn in place! But the nozzle on the T500 “gears” the motors for high thrust, low speed. Whatever your maximum speed is, can likely be reached with (or without) considerable extra drag / payload added to your craft…
To achieve faster speeds, you need to reduce drag and increase the “prop speed” that the motors will move water at. Removing the nozzle turns the thrusters into "M500s - a product that is actually launching fairly soon (with better mounting options than a modified T500.) A M500 prop will also be launched - this combination may be able to reach 4 m/s, or at least faster than the T500s! A launch date has not yet been set, but I would expect before the end of Q2 '26…
If you can’t wait that long, checkout this link! With those props and nozzles removed, the BlueBoat just barely can achieve 4 m/s. - using about 1.5 KW to do so!
The nozzle-as-gear analogy makes a lot of sense, and the M500 is definitely on my radar now.
One thing I’m still not sure about: with a small-diameter, high-RPM prop running close to the surface, I’d expect ventilation and cavitation to be a real concern — especially in any chop or during turns. Is that something you’ve seen in practice with the T500 on surface hulls, or is it less of an issue than I’m imagining?
Also — thinking ahead — is there anything in the Blue Robotics lineup (current or upcoming) that offers more power for surface applications, beyond the M500?
And last, out of curiosity: do you know of any USVs in a similar size class — 2–3 m hull, 200–300 kg — already running T500s in the field? A reference build would be really useful.
Hi @madro -
Ventilation is certainly a concern - cavitation typically can be avoided by prop design, especially if the diameter is small? The mounts linked for the M500 adaptation of the BlueBoat lower it significantly, and by having the weight that far back makes the boat really pitch backwards when udnerway, so ventilation wasn’t too bad - the hydrodynamic shape of the hull helps significantly!
Higher power options are not on the near horizon, but significant upgrades to durability are coming with the major thruster revision in the works!
I’m aware of folks who’ve built vessels in that size range, but don’t have example footage or design, performance details. Sorry!
I see you’re releasing new versions of the M500 soon. I’m working on a project and was planning to buy the BASIC ESC 500 speed controllers to build it.
Will you also be releasing an update for the speed controllers?
Hi @jua123 -
There is no ESC update planned in conjunction with the M500 launch. An ESC is being worked on, but it’s at an earlier stage of development, relatively speaking! That ESC will have a similar capacity to the Basic ESC 500, and include lots of amazing features targeted at general robotics and marine applications.