Mostly likely the hockey player will win on the ice, regardless of how good the boxer might be. Balance on skates is a whole other ball of wax and it would completely throw off a boxer to have to throw punches on the ice.
I played junior hockey and also earned my Golden Gloves as an amateur when I was 17. I've been in more fights than I can count and can say, from experience, that most hockey players (even goons) don't know the first thing about how to properly fight. But all that changes once you hit the ice. It is such a different way of fighting that, if you don't boast the balance and strength of a hockey player, you're going to be a fish out of water and will likely get smoked.
But, if we're talking off the ice, the fight would last about as long as the boxer wanted it to last (ie. the hockey player would be drinking through a straw by the end of it).