Your battery may be able to crank your 150, but that may be all it can do.
Just because the voltage is within specs, it doesn't mean there is adequate current flow (amps), to run your 3 sonars when the main motor is cranking.
Check the obvious first:
Fully charge your battery and have it load tested.
Places like autozone/advanceauto will do it for free.
If that is not it, then the Onix may indeed be very sensitive.
I'd get a separate battery for the 3 sonars.