4.3 i/o runs for a moment then dies out...

I hooked up one of my dual batteries backwards and caused a mess after turning my selector switch to the reversed battery on my 2000 4.3 liter volvo penta i/o carbureted "GL-PEFS" model. The engine compartment smoked and the motor now will only run for a moment and then go dead. I can start the motor over and over w/ no issue but it will only run for about 10-15 seconds and then stall. I have had to replace the terminals on the batteries because the negative terminal melted off both. I have also replaced the selector switch because it was fried, other than this there is no obvious damage. Does anyone have any guesses... alternator issue maybe? Any help is appreciated.

Re: 4.3 i/o runs for a moment then dies out...

So far I have jumped the fuel pump relay and now the boat will remain running. This tells me that it has to be due to the circuit from the alternator that should pick up after the starter to keep the fuel pump running, this will be voltage or diode problem. My only issue is the alternator has so many wires on the back and most of the schematics I see speak of a "green " wire from alt. to fuel pump relay. I have no green wire on back of the alternator or at the fuel pump relay... So it looks as if I will have to unwrap the whole harness to trace the wire and diode unless somebody else has another idea or maybe a pic of the back of a similar alternator which will directly point out to me which alternator stud/wire it is that feeds the fuel pump after the starter... pretty please