Mag 350 idleing issues

I have a 2006 Mag 350 Ser# OW389906. It has a Bravo III drive and is in a Crownline 240EX. Here is the issue:
New problem, never happened before. When I start it first time for the day, it will start right up and sit and idle for a couple minutes and die. After it warms up it cranks for about 5 to 10 seconds before it tries to start and finally starts and dies immediately. However, if you put it in neutral and give it a little gas, it will start and if you keep it revved up above idle, it will run all day. once back to idle it dies. It doesn't die like a switch is activated, it dies slowly if you know what I mean. Or, if when it starts and you put it in gear and give it gas, it will run fine all over the lake.
The oil pressure is at 70#, temp is 180, fuel full, voltage fine. Fresh water lake it's whole life in Lake Norfork in Arkansas.
Thanks for the help. This forum is a lifesaver.

Efi or carb?

kghost said:

Efi or carb?

Click to expand...

It is EFI I think. I know it has a low and high pressure pump and a fuel rail so I think that means EFI?

Poor idling is sometimes a vacuum leak. Be sure all the vacuum and other manifold hoses are in good shape with no cracks or splits. This means at idle, it is getting too much unmeasured air into the engine, therefore causing a lean condition. Usually a simple fix to replace a hose or whatever.

I will check for air leaks this weekend.Thanks so much!!!