What in the world would cause the engine to run up to 4000rpms, 33mph and run just fine one day, then the following day wont go above 3000rpms and 11mph? Cant even get it on plane. trim tabs are up, no drag. trim outdrive to standard position but nothing. im changing plugs, fuel filter, rotor and cap next weekend, but for the life of me i cant see where this is the cause. i would think that it would run in one condition or another full time. havent put a scan on it yet, just going by past engine experience. Any suggestions?
6.2 mercruiser problems
- Thread starter Dadsturn
- Start date
Jimmy Buoy
Well-Known Member
- Dec 3, 2008
- 2,464
- Boat Info
- 2003 Cobalt 293
- Engines
- Twin Volvo-Penta 5.0 270hp & DuoProps
From your description is might be that a sensor might be triggered and the computer has put the engine in limp mode. Are there any warning beeps, or do you have a smart craft readout?
i have a single beep that comes on randomly when it does this.
Jimmy Buoy
Well-Known Member
- Dec 3, 2008
- 2,464
- Boat Info
- 2003 Cobalt 293
- Engines
- Twin Volvo-Penta 5.0 270hp & DuoProps
Time the beep with a stopwatch. If it's one beep every 60 seconds I think that indicates low water pressure on the raw water pump. Had the same thing when I launched in the spring but it would come and go while I was heading out from storage for the hour long cruise at 1200 rpm to the St. Clair River. Must have been some crap stuck in the sensor because once I got underway in cleaner water the beeps stopped and the boat operated normally. I have inboards but you have IO's which may be experiencing a restriction in the water hose coming from the outdrive, or it could also be your pump housing worn with wear grooves & not pulling enough raw water through to cool the system.
You might locate the sensor on the raw water pump and unplug it or bridge the two wires to see if that makes the alarm and limp mode disappear. I can't imagine it actually overheating when it ran fine the day before. Check your temp gauges too!
You might locate the sensor on the raw water pump and unplug it or bridge the two wires to see if that makes the alarm and limp mode disappear. I can't imagine it actually overheating when it ran fine the day before. Check your temp gauges too!
skibum
Well-Known Member
I think you might have one or more spark plugs not firing. Check your wires to make sure they are tight.
Sorry, have been gone. the beeps are not in time sync. but they come on when i am underway.
going this weekend to replace plugs, cap and rotor. have a tech that will be going this week to get codes to what sensor is making the engine go into limp mode. I have the smart system, but i cant read the digital readout. ordering a new gauge for that.
