The TAMD42,43, and 44 along with the sterndrive equivalents use a cutoff solenoid to disengage the supercharger clutch at around 2200-2400 rpm. From there, the turbocharger only provide the forced induction. It is common out here on the West coast to wire cutout switches to the supercharger clutch solenoid, as it always seem to come on when it is least needed, e.g high speed trolling on some hulls. The switch prevents the blower from coming on when it's not wanted or needed.
The supercharger is primarily to help heavier boats get on plane, when turbo boost alone would be insuffucient to get the boat on step.
The supercharger assembly uses it's own oil supply reservoir, not common to the crankcase and must be changed seperately.
These are very good engines although some would say a little too complicated.