Thinking about installing a 2000watt Power Inverter to run a 1000W (1350W @
120vac consumed) microwave oven and to heat my hot water tank 1200W @
120vac not at the same time.

Or to use a 2KW portable generator.

When heating the water, I estimate that the run time is about 20 minutes to
achieve max temp.

I'm wondering if my house batteries could handle the additional load of an
inverter.

My boat has a 300HP outboard with 60-70 Amp alternator (i cannot increase or
change the alternator)

help is neeed for an old "Duffer"