Unimproved 4-4 River Call

This guy has been playing very aggressively and has been in alot of pots with trash hands (ex. calling a 4bb raise with J4o). I called on the flop here to keep him honest and to see how he acted on the turn. After his turn bet, I was pretty sure he was messing around.

Anything wrong with this? Should I raise in any key spots?

***** Hand History for Game 4395239137 *****
$50 NL Texas Hold'em - Monday, May 29, 23:08:54 ET 2006
Table Table 108169 (Real Money)
Seat 6 is the button
Total number of players : 6
Seat 1: robj204 ( $50.65 )
Seat 2: The_Saint80 ( $62.70 )
Seat 4: zic25 ( $62.17 )
Seat 5: barrettrg ( $80.17 )
Seat 6: zaaaaaak ( $65.98 )
Seat 3: brownbulge ( $24.50 )
robj204 posts small blind [$0.25].
The_Saint80 posts big blind [$0.50].
** Dealing down cards **
Dealt to zaaaaaak [ 4c 4h ]
brownbulge folds.
zic25 folds.
barrettrg folds.
zaaaaaak raises [$1.75].
robj204 folds.
The_Saint80 calls [$1.25].
** Dealing Flop ** [ 3s, 6h, 2d ]
The_Saint80 bets [$3].
zaaaaaak calls [$3].
** Dealing Turn ** [ 3d ]
The_Saint80 bets [$6].
zaaaaaak calls [$6].
** Dealing River ** [ 8c ]
The_Saint80 bets [$11.93].
zaaaaaak calls [$11.93].

You're saying he's calling with bad hands but is he playing them aggressive? Ex. betting out totally empty, etc.?

If he called a raise with J4o then he could have literally any piece of that flop, from 45, to 83o, to 23o. This hand is entirely read dependant.

Raise flop. Even if he has garbage, you are not ahead by much, and if he does hit one of his outs, chances are you won't see it coming. This is a great flop for you, but you really need to protect your hand.

Probably raise flop and take a free card on the turn if called.