Have a 502 engine with a 4 barrell carb. Boat was running fine and the last time I went to use it the engine will not idle. I can get it to idle down to 900 rpms but anything lower than that it stalls. Checked the fuel filter and it was ok. Where do I go from here?

Carbs? I've had to make adjustments to mine over the summer.

It could be a dozen or so different things. If it runs fine other than at idle, its probably in the carb.

Remove flame arrestor and see if theirs any fuel dumping out the j tubes..may have a piece of crap stuck in the needle and seat..

sounds like a vacuum leak or the choke needs to be adjusted, did it just start this all of a sudden ? runs fine otherwise ?

Make sure:

Blades are shut on the primaries and sec.
No air leaks
stuck needle and seat (wouldn't run even at 900 rpm but check anyway)
powervalve leaking
check timing
check plugs/wires/dist cap and rotor not likely if not missing

How long did it sit before your last run? Was it cold weather when you started having problems? Did you let it warm up and see if you had the same problem?

900rpm idle sounds good to me.

If it is a QJet, it has dirt in it. They hate dirt and the idle clogs up. take the top off and clean out all those little holes.

Sea foam fixes all

my boat will idle between 600-900.shoot for something around there.depending on the temp and humintey the idle will change.