496ho intermentent issue
 

Need help!!! 2006 35 Outlaw 496hos port engine having issues running. Boat will run perfect right off the trailer but after sitting in a cove for a few hours port engine will start but as soon as I put it under a load it just falls on its face. When given throttle, rpms jump all over and you hear and internal pop almost like a back fire. Boat has also done this after only running a few minutes so don't feel like it's a heat issue. Yesterday we coved out 6-8hrs after running about 20 minutes and it wouldn't run. Stopped scanned engines and then it ran fine all the way down the lake.

Things we have tried:
Scanned engine and no codes except for see below using Rinda TechMate Pro
Replaced spark plugs
Replaced IAC motor
Replaced fuel filter
Checked fuel pressure at idle and running 43psi
Compared outputs on both engines

When scanning I compared every single output and the only output that was not the same was the IAC % at idle. Problem port engine runs 20% at idle and starboard runs 0% at idle. Port ran about 50% at 3000 rpms Also, I did have a Map sensor code but it has since disappeared.

Anyone have this happen or have an idea what to look at?

Might be plugs or wires. Was working on a friends HO (single engine) and it got so bad it wouldn't even get on plane and there were no codes. Only thing was the IAC and timing kept moving. Used the scan tool and did a misfire test. The test showed there was one cylinder which was not firing correctly (little to no change in rpm when cyl was selected).

Replaced the plug and wire, and IAC and timing settled down.

We did the misfire test and everything cut out like it was suppose to.