57 GSi drops back to idle

"I have a 1999 5.7 GSi that ha

"I have a 1999 5.7 GSi that has started to cut back to idle somewhere around 3000 RPM. The first day this happened, after returning the throttle to a low position, I was able to run for the rest of the day without problem. Now, I can't seem to get above 3000 RPM. Once this RPM is reached, the boat acts like I returned the throttle to idle, even though I haven't touched it. I can reduce throttle to a low position and and accelerate back to anywhere below 3000 RPM. I find that when I initially take the boat out it works fine until it warms up. When the problem occurs the temp guage is reading around 175, oil pressure looks normal. The engine runs great at high speed until this problem occurs and runs well below 3000 RPM after the problem occurs. I changed the fuel filter and disconnected and reconnected all of the electrical connectors on the engine that I could find. This made no difference. I'm guessing that I'm running into some kind of fail safe condition. Where should I start looking for this problem?"

My guess is the Engine Protect

My guess is the Engine Protection Mode temperature fail safe that kicks in around 2500 rpm; usually with the audible alarm but not all systems have the audible alarm. I think it triggers the ECM around 195- 205 degrees. I would perform normal cooling troubleshooting as your engine should be running in the 158-194 degree range and gauges aren't always accurate indicators of the true temperature.