Rough idle

[curfol]

After about a 3 hr cruise at around 2800 rpm , I throttled down to idle and starboard 7.4 died . as I started it , she fires right up but idled exactly up and down up and down. I finally got it in the slip and let it cool down about 3 hrs. Same thing when I started back up. And then about 12 hours later when we headed home. Once at speed it ran fine. But it won’t idle anymore.
Any ideas would be greatly appreciated.
98 400db 7.4 efi
Thanks

 

[Jimmy Buoy]

Idle Air Control (IAC) that is no longer working can cause these symptoms. Water leaking from a manifold into the exhaust valve area can also cause the engine to have a lumpy idle. My money would be on the IAC.

 

[curfol]

Idle Air Control (IAC) that is no longer working can cause these symptoms. Water leaking from a manifold into the exhaust valve area can also cause the engine to have a lumpy idle. My money would be on the IAC.

Thanks I’ll check it out. Have any idea where it’s located