Weevil and his mother didn't even know they were being targeted by the marines until they got to them, unlike Mihawk in a desert island who read the news and found out about it before. So we can see here that Weevil and his Mom aren't very well informed people.
So if Weevil didn't even knew of the end of the warlords system, there's no way for Weevil to know where Marco is unless they go the island, destroy everything there and torture people asking for his location.
And even then, last time we saw Weevil, he was in some island in the new world fighting marines, not even close to Wano, and if he went to Wano, Onigashima would already be up in the air, considering most people that get to Wano crash on the beach for a day and break their ship, even Prime Whitebeard.