5.0LX Surging at Idle

[brown_tx]

I have a 5.0LX (SN#OF27759) its around a 94 model and has a quadrajunk 4 barrel carb on it and it is surging at idle. It is going from about 800 to 1000 rpms. You can see it on the tach, here it and feel it in when Idling through the marina. I recently bought this boat and have had to go through it from top to bottom (thanks to these forums for guidance) and for the first few outtings it ran fine, Although I have not really pounded on it too much. I have drained all fuel after purchasing the boat as it was a couple years old. Change fuel lines, filters(yes I got the one in the carb), plugs, distributor cap, wires and rotor, oil change, drained lower unit and reservoir of drive lube and replace and replaced the impeller. I am thinking the only think left to change that could cause the surging is rebuilding the carb, but wanted to bounce it off you guys before I tore into it.

Thanks

 

[NHGuy]

Re: 5.0LX Surging at Idle

Rebuilding the carb is not a bad idea, but here are a couple of easy checks, things you can do.
Remove the spark arrestor and hold it up to the light, it may be clogged. It can be cleaned with some spray carb cleaner. Check the carburetor hold down bolts and the intake manifold bolts, make sure none are loose. When the motor is running shoot some bursts of carb cleaner in the primary side. Do this at a higher RPM than idle, and don't use so much that you stall it out. If you accidentally DO stall the motor leave the carb open to the air with the throttle open and give it a few minutes to let the fluid evaporate. Don't start it up right away after you've drowned it, that can cause hydrolock damage in a very small percentage of situations.
If you suspect the intake manifold gasket or the carb base gasket shoot a little carb cleaner there, if the motor picks up speed there's a leak.
Good luck, maybe it is the carb, but these things ought to be checked every so often anyway.