You guys certainly have a point on the emissions.

Get used to it, it is not going away. As emission laws get tighter, pretty much everything will be forced to go to it to comply. Plus, the greatly improved performance and fuel economy makes it a slam dunk. Regardless of any other issues, nothing would EVER make we want to go back to a carburetor and distributor on anything!

Tom

They are relatively new.

Tom

I have seen something as simple as a temp sensor doing what you describe,,,,, only dif being is is held a high idle on top of your simptoms,,,,not chocked it which leads me to belive the problem is after the controled circuit,,,,, also,,,,,, is there a ground cable between the two motors?

Another thought,,,,, do you have seperate tanks, or does both motors draw off of one tank?

They draw off of separate tanks but it does not act at all like a fuel problem so I don't see that as an issue. And yes, both engines have a common ground.

It acts like something is suddenly telling the EFI to dump in many times more fuel than is necessary or normal. If the engine happens to be at idle at the time it happens, the idle speed doesn't change much it just starts running very rough. The odd thing is that the problem goes away and stays away if I keep the engine at about 4K or above.

Check all your grounds including those at the bell housing. also if you have not changed your cap and rotor yet change it. these engines are very sensitive to cap and rotor wear or corrsion.

Just a thought, try checking you timing under load, with the scan tool and a timing light, if the timing isn't correct replace the distributor the whole thing. Mark @ Precision Marine mentioned this to me about 2 weeks ago I was doing some troubleshooting on a 575sci

once a good tuneup is verified,,,,, I would also change the fuel water seperators.

next Id lrun the boat with a scan tool hooked up,,,,, save you alot of time and potentially money of guessing and throwing parts at it.

There is always the old way of swapping parts between engines,,,,,, but thats kinda hackish IMO

The problem turned out to be a bad computer. Now all I have to do is try and find a 861720T2 EFI-3...

Thanks for the help!

Tom