Hi @hotrocksunday -
Welcome to the forums!
While we haven’t conducted testing at those depths directly, it should be possible to use at that depth for indefinite duration without any issues.
The important thing that must be done to operate deeper than the rated depth is adding a connector to the cable going to the thruster (like one from BlueTrails Engineering, which also sells the T200 with connector already attached.) The likely failure mode below 300m is water finding its way past the potting compound that seals the end of the cable to the stator windings, and if using a WetLink Penetrator, this water can pass thru the cable and into your housing!
A connector stops this, but may lead to some voltage “leaking” to the water, which can impact performance slightly and reduce efficiency - far less than some sort of housing filled with oil would! Since the T200 is fully flooded, the modification you describe isn’t really going to be possible, but perhaps the M200 could be used to accompish something like that? We’ve had users operate at 1000m for 1.5 years + off the coast of Monterrey bay. We heard an update on this in the last of the StreamFest episodes!
I’m curious why 316 Stainless Steel wouldn’t last long in your application? Typically it’s one of the best materials for corrosion resistance….
I’d argue that Blue Robotics can be considered “major” as there are over 6000 BlueROV2s in the world, and likely more T200s than any other subsea thruster type ever made in existence!