engine idels at 3000 rpm when i start it.

[pgt819]

I have a 2004 chev 5.0 mercruiser stern drive that is ideling at 3000 rpms any suggestoins on what might be the problem. I tested the motor at home before I went out. It started ran great souned good to . Then got it to the water started it and ran good until a gave it some gas then the alarm went off . It was still ideling fine then . Checked all my fluides they looked ok then checked temp volts and oil press all were normal. So took it out of the water got home and started it to see if I could find the problem no luck. And now the engine when I start the boat shoots up to 3000rpms. Any suggestions would be a great help. Or even if you know a good boat mechanic all the ones I find don't ever fix the problem.

 

[WoodieMan]

Need more info; is this EFI? Disconnect throttle cable at engine and light her up. Does the problem go away?