Did the fuse not blow again? It does need the fuse in order for fuel to travel up through the carb and into the engine. The first place I would start on this is remove the connector at the voltage regulator and see if the fuse blows again. A seat switch can cause the symptom of stalling when the clutch is released, but won't blow the fuse. Posting the model # from below the seat would also be helpful. 917XXXXXX

I also was bit confused??? brake pedal switch IMO won't blow the fuse either if it has one??? If the fuse is still blowing I would also try to unplug the elect. clutch if it has one??? This may narrow it down to the elect. clutch or the PTO switch if the fuse doesn't blow after diconnection of the elect clutch harness at the clutch assy.

The only 2 GT 3000's I have in my database have 21 & 23 HP engines, but are Kohlers.

I'm guessing that the GREEN wire from the ignition switch, to the seat switch to the OPR is shorted.

Both schematics show that they have an Operator Presence Relay.

Disconnect that and see if it still blows the fuse once you have verified the Green wire isn't shorted.

As mentioned, the Sears 917 # can be useful to make sure we are looking at the correct schematic.