Reverse polarity when powered by aux generator

[3rdOrderEffect]

Ok, I am stumped here, altho I suspect I am missing something simple.

My boat has a diesel genset that works fine. When powering the boat via the genset, I do not get a reverse polarity indicator on my selector panel or the ac breaker panel.

When I plug into shore power (boat uses 30A), I do not get reverse polarity indication either (has worked fine at every marina I’ve been to).

Now when I plug into the auxiliary inverter generator I bought to backup the main genset, I get a reverse polarity indication no matter how I wire the adapter. I am using this adapter to convert the generator’s TT-30P output to the boat’s L5-30R shore power cord

I have ensured the female side of the adapter that the shore power cord plugs into is wired to standard

But because I was getting reverse polarity indications I rewired it with line and neutral swapped and got the same results. I swapped it back.

When powered off this inverter generator, I immediately get a reverse polarity indication on the ac selector panel (right side of photo), but I get polarity ok on the ac breaker panel (left side of photo). However when I turn on the battery charger, I now get reversed polarity on both panels. Again, this happens no matter how the adapter is wired

What am I missing here?

 

[SteveK]

Have you used a voltmeter and with shore cable plugged in identified the outlets, then compare to the gen outlets to see if they agree with your drawing?
2nd thought, shore, inverter and main GEN have ground & neutral bonded. Maybe the portable one does not bond these and that results in the reverse light.