Thanks to all. I still seem to have ground connection to these circuits fed from marina A.C. For each receptacle: test light in neutral and line gives light. In line and ground gives light. In neutral and ground I get no light. I'm no electrician (got the method from YouTube!!) but think that shows receptacle works but the GFI function is no longer. Was at another marina last few days ... plugged in and ran heater etc just fine but lights still flashed so it's not my current marina's problem.
I was at Running Room last week and heard one runner say he was once electrical contractor. Asked him about this. His view ... a power surge after the power failure would have cooked these GFIs.
Good idea to buy one and try it. I'm in B.C. and don't always get the same variety of bits in Canada as found in the U.S. but I guess can always mail order. I've asked many sailing friends and they haven't seen such a fancy GFI here .. the Beneteau was made in Marion S.C.