Originally Posted by carcrash

The problem with EFI is that all the signals go into the computer, and the computer then adjusts everything. If any of the signals are a bit wacky, the engine runs wierd. It is IMPOSSIBLE to determine the source of the problem from the symptom.

Teague could not do it. Paul Pfaff could not do it.

I eventually had Pfaff simply replace the entire wiring harness -- easily ordered from Mercury by the way. The harness plus installation cost about as much as 10 brand new Holley marine carbs, or a pair of new CMI headers.

Inspecting the old harness showed that a few pins in several connectors -- and different pins in different connectors between the two engines -- were corroded. This caused the signals going to the engine computer (fuel flow, air temp, knock sensor, etc) to either be slightly off or inconsistent. This also causes the controlling actions from the computer (throttle setting, timing, fule flow, etc) to be wrong or inconsistent.

After replacing all the wiring harnesses, the engines again run perfectly. My boat is only 7 years old. Some of the problems that have been fixed by the new harness were inconsistent problems that Teague and Pfaff were not able to fix for the past 4 years and tens of thousands of my dollars.

Right -- most of the time, my EFI engines have been giving me wierd little problems.

The total cost of all the attempts at fixing what was really due to corrosion in the wiring harness exceeded the total cost of two new 454 Magnum EFI engines.

With carburated engines, its very easy to figure out what is wrong. And hardly anything ever goes wrong, and if it does, its very cheap and easy to fix. Any idiot, even me, can fix it.

With EFI, you can't accurately isolate the problem, all the parts are very expensive, all are prone to glitches (sometimes its OK, sometimes its not) and the best mechanics in the industry may well not be able to fix it no matter how much money you throw at the problem.

EFI never again.