Playing 1/2/3: SB is $2, BB is $3, and the button is $1.

The table is loose and relatively passive; I'm frequently seeing 5-6 callers make it to the flop...

...except if I raise. I've been there for a couple of hours and am seen as tight and straightforward; I've recently taken down several hands with preflop raises or bets, and everyone tends to fold to my aggression. SB is a bit loose preflop but seems able to fold after the flop.

$1/2/3 NL (8 handed)
MP Hero ($450)
SB Villain ($400)

Hero is dealt J9

2 folds, Hero raises to $15, 3 folds, SB calls, BB folds

Flop (~$30)
853
SB checks, Hero ???

Welcome to the forum, OP.

Gotta bet flop, imo. Another diamond will kill your action or your hand., If you bet now, you'll get a call from sets, the bare Ad or Kd, and maybe lower diamonds, especially if the they are part of a PP.

If you get called on the flop, V will likely also call a blank turn to draw, especially if it gives him a pair greater than 8 to go with his diamond.

Get value now, because the only way you're getting value OTR is if you get outdrawn.

Bet $20 on the flop, $50 on blank turn, and as big as you think will get called on river blank

Bet flop to get called by 2pair/sets/FDs or smaller flopped flushes and Ad/Kd

slowplay might be bad here at passive table

A little odd that a loose table that has lots of people that like to see limped pots is also at the same time tight facing a raise. I think opening this hand in MP is a little loose but it seems your table is tight enough that way, and we got the desired/expected result (HU, in position, with initiative), so fine.

SPR is ~13 on the flop, which means that we can play for stacks with 3 PSBs. In this raised pot, I'm prepared to play for stacks with this hand unless the board runs out bad. So my plan would be to PSB each street and probably never fold unless a fourth diamond came (or perhaps the board paired with Villain giving lots of action). ETA: Just realized the question was whether to slowplay; as others have stated, absolutely not (for the reasons others have already given).

GcluelessNLnoobG

You shouldn't slow play here, or think you should have if you bet and they all fold.

I bet pot on the flop - V's calling ranges on the flop are going to be completely inelastic, so make them pay to see their 4th diamond. If you get raised, play it as fast as you can.

I think it can be OK to slowplay if someone else is showing aggression and you are just calling instead of raising, but that is not the case here. Don't waste a street. Later cards will tend to make it less likely, not more likely, that Villain will give you action. Bet.

This is my ''auto pilot'' too. But we can do much better as the posters below explain. Our 2/3,2/3,1/2PSB line wins $170 when villain has something. Their line wins $400. These kind of hands are what separate modest winners from crushers.

Thanks, glad to be here Yeah, I think you're all right. I slowplayed this in person, but felt like a moron immediately after the hand ended because so many things can go wrong: a fourth diamond can beat my hand, paired board, etc. And as several people mention I'm leaving money on the table if villain has a set and is willing to call 3 pot bets.

Never slow play 3 flush or paired boards, that's what most players expect you to do