IAC has already been replaced with new, didn't fix anything. I troubleshot it originally, if I covered the hole in the secondary butterfly, the motor would stumble initially and then the IAC would open bringing in the alternate air. So even the old one was working imo. I'm thining it is a sensor problem that will have to be diagnosed with a scan tool. Something i may invest in if i plan on keeping this boat for a number of years. But for now, it's at the shop.

Did you check the area where the IAC seats. Although the IAC may be working fine, if it can not seal good against its seat, it will not close all the way. This is usually the problem with them. IAC's themselves rarely go bad. It is usually a buildup of carbon in the throttle body that stops them from closing all the way.
Eddie

Eddie, i think he has the older style IAC where the plunger seats in its own housing(ford style iac) not like the newer style merc efi engines..

I had pulled the throttle body off and cleaned the whole thing down. The venturi the iac plunger goes into was clean. It is just a metal on metal contact from what i saw, and it was clean before and after pulling the body off.

check injector orings for vacume leaks!....

I never pulled the fuel rail. Just the plenum. Either way, here is an update from the shop:

Basically they verified what i had found, that the base timing was high at 14 degrees. They don't know what changed that it got there, but all they can tell me is that with the scanner on, and put into base timing mode, it was high. They put it back to 8 degrees, but liked the way the engine idled better at 9 degrees. They are going to do some more checking on other sensors and such, but they believe the timing is the whole problem. I would sure like to know how it changed. There was no way that distributer moved, the bolt was tight when i checked it.

I could have left it at 8 degrees as well, but I didn't see how if it was set at 8 before, it changed to 14 without some sort of sensor or something made it go to 14. I am being told that in base timing mode, outside sensors are no longer an influence. So, they are leaving it at 9 degrees.

water temp,,,on the goose neck,,,, unplugging it is what makes it act up,,,, check the pins to make sure they didnt pull back

Gotcha! how many hours on the engine?timing chain slip?

I tried that as well. No problems found with it............

20 hours, max........... Just rebuilt last fall.