In addition to what's been said already - if you check on the ranked leaderboards you can see how many times (if any) you've won each race.
Make a note of which you haven't won yet so that on the odd occasion that you do get control of the room you can put it on one of those races (assuming you don't get majority booted when people realise you've chosen a boat-race!)
Good Luck.
EDIT: The ranked leaderboards I refer to above are on the Rockstar Social Club website, not in-game, & can be reached here...
http://socialclub.rockstargames.com/