rough idle

[2000superair]

ok let me start out saying I feel like an moron. I forgot to poke the drain holes on a 2000 super air 5.8 gt40 and it froze this past winter. I drained everything else and turned the valves and shut the hatch. I know I know I know. well the freeze plugs popped one on each side in middle. changed all six out and checked oil. no milk no sighn of water in oil no oil slik behind boat or in exaust. I have put 6 hours of good riding on this motor sense. still no sigh of water in oil so no cracked block. checked all plugs no rust. pulled valve covers oil looks like I just changed it as did the dipstick so no cracked head. I noticed this past weeknd that only at idle dose the boat have a stumble or shutter at idle or when you just put it in gear. after you start giving it throttle it goes away. it is noticeable only at idle changed plugs changes distributer cap and rotor buttin still has vibration that you can feel in drivers seat at idle not terrible but noticeable to my wife and I sense we spend about 150 hours a year on it any sugestions also to add this past year it had miss fired a few times running about 3/4 throttle acrose the lake but hasn't sense my thought was on this bad gas but what are the chances it could be out of time other than idle it runs great

[ski4evr]

You're doing the right thing eliminating the simple first. Vacuum leak? Its messy, but WD40 sprayed on a cracked vacuum line will increase the rpm while running if you find one. Plug wires ok?

[s_kelley2000]

When is the last time you changed the fuel filter in the FCC? Might want to do that if it's been more than a season or two. Glad to hear you dodged a bullet on the frozen block.