[neto]

How many battery banks do you have? If only two (Engine bank and House bank), try tracing the starter wire and verify its connected to the same place your other engine's starter is taking the juice... It could be that that specific starter is connected to the house battery bank and those deep cycle batteries have much less cranking amps to start an engine, much less a 450C. If they are indeed connected to the same bank, then my next move would be to clean terminals and try again. What starter do you have? 38mt or 42mt?