SlowBro,
The inverter is too small IF the converter will go to bulk charging mode.
The WF-8945 draws 780 watts or 11.6 amps @ 120 volts, when running flat out.
11.6 amps @ 120 volts = 116 amps @ 12 volts.
Sizing the inverter suggests that 1000 watts might be a better fit.
C/8 is the acceptance rate of a lead acid battery at 85% state of charge. If it is at 50% that may be a LOT higher.
Most alternators have a duty cycle of 2/3, so if the battery bank is "hungry" the alternator may let out the magic blue smoke, with the caveat that the cables to the inverter are thick enough to handle that much current.
On the other hand, WF converters are FAMOUS for not going into bulk charging mode. In that case the 800 watt inverter would not over load, nor would the alternator fail.
It is far better and probably cheaper to use a dc to DC converter between the alternator and the battery bank. That way charge current may be set where you want it.
Do a short time test, preferably with the house batteries cycled to 50%.
If the voltage drops to 12.7 on the engine battery STOP the test.
