Thor's made Maxam his *****. I mean treated him like a child. Of course Thor's almost never in that mindset.
So in this fight, they probably brawl, with it being a good fight and Thor taking it eventually. I recall Maxam stalemating Hercules and beating him by tossing him into the ocean in a brawl during the Infinity Crusade.
Hammer or no hammer, Thor is still above Maxam physically.
Maxam is still ridiculously strong. He equals Dumb Drax's strength pre adrenaline levels. Whether the Power Gem was taken into account with those calculations I don't know.