2004 Nordic Heat with a 496HO that I just rebuilt and added a Whipple kit to. I've run it on the trailer a few times and everything was working great. I was installing an updated Lowrance this weekend and after I got the old one out (it was not connected to the smartcraft) I tried to lower the power engine hatch and the switch didn't do that, it caused the Aeromotive fuel pump to run! Both directions of the momentary toggle switch would run the fuel pump. I tried other switches on the dash and the bilge, blower, and some light switches also ran the pump and not the function they were supposed to. I know all these had worked since the engine install. The drive trim and bennett trim switches function as they should. I replaced the batteries tonight and that didn't fix it. The Whipple system uses the stock fuel pump harness to trigger an added relay to run the pump for those that don't know. The key switch will run the pump for 5 seconds as it should, and turning further will crank the engine over as it should. I did notice when I turn the key on the Livorsi oil pressure gauge pegs itself and stays there. I'm not sure that's normal.

I'm baffled here, the old Lowrance system had a power and ground and was independent of the engine. Thoughts guys?

You've lost a ground somewhere.
Gonna have to retrace your every move. Probably knocked something loose.

We fixed it today. Thanks for the help guys! My friend brought a tool called a power probe and he figured it out in a few minutes. The ground at the fuse box wasn't good. So we ran a new ground wire to the fuse box from my 4ga stereo ground wire nearby. Everything works great now.