Thanks Ant
My attempt to ballast last week failed due to a badly fitted bow thruster leaking.
This is now sealed in a much simpler fashion and removal only requires a scalpel
I've just tested everything dry on the bench and found one steering servo has and internal mechanical fault, it rotates freely clockwise but very high resistance anticlockwise.
I ran both props to full speed and they make one hell of a draft
Anyway tomorrow I'll try again to establish full displacement weight and I can run one motor to find full load current.
I'm temporarily using a Spektrum radio and the bow thruster is on Aux 3 pos switch B