Hi, and welcome. It's good that your fiance is aware that he is drinking too much. it doesn't sound as though he wants to stop, however. THAT is whole nother ball game. I wouldn't marry him at this point. Life with an addict is no picnic. It's easier not to go there than to try to get out later.
If you have not already, I would pick a time when you are calm and he is sober and alert--not hungover. I would express my concerns about his consumption and, if you decide to take this route, tell him there will be no marriage unless he stops drinking.
And mean it. That is your boundary.
Watch what he says and does when you do this. That will go a long way toward telling you where the alcohol is in his priority list, and where you are. Peace.