This was an interesting hand. I'm still troubled by my turn decision...

Oceans 11 game with a max buy-in of $300.

I have a stack of about $420. MP1 seems like a fairly straight forward T/A player, and has about $500, MP2 is a loose/passive guy who's on a rush with about $900, the cut-off is new player with $200, and the button is a loose aggressive player with about $300. I've been at the table for about 2 hours and I have a general impression of these guys, but no great reads.

I'm under the gun with black 6's. I limp for $3. MP1, MP2, and the cut-off call. The button bumps it to $10 (he makes pot-sweetening raises to $6 or $10 almost any hand he plays, though the normal table raises are around $15). The blinds fold and everyone else calls.

The flop comes
Qd, 6d, 5c

At this point the pot is a little over $50. Most pots are underbet in this game, especially on the flop (unless the pot was limped, and then it's overbet....). I bet out $50 with my middle set. I didn't want a diamond to draw cheaply, but I wouldn't mind a queen raising me... All four players call the $50. Now there is $300 in the pot.

The turn is the Td completing the flush draw. I check, MP1 bets $75, MP2 calls $75, cut-off folds, and the button folds.

Now I have to decide whether to call or not. With four callers on the flop I KNOW that someone has the flush, and I'm pretty sure it's MP1. But what does MP2 have? He's loose, passive, and loves to call, but these are fairly big bets for him to call with just a pair. The pot is now $450 and I have to call $75. Do you draw at this point? How many outs do I likely have?

That's ridiculous. If his read is that one of them has a flush and the other has at least two pair then calling is obviously the wrong play. Of course you can't be looking for monsters under the bed but if you think very strongly that the opponent has it, then you have to play under the assumption that he does.

Theres no way you could ever have a that strong of a read of 2 pair on that board when you have 3 of the 6s covered. Basically it HAS to be QT and only QT. Im not worrying about Q5.

Call and get to showdown as cheaply as possible...consider folding the river if you don't fill up. However, it's hard to do that live

You're still worried about the weaker two pair as it takes your outs away. Also a set is pretty possible here from a loose passive donk.