So, I brought my boat to my mechanic for a routine service, and an intermittent problem cropped up that they are having difficulty troubleshooting. I am hoping someone has seen this before.
Here is what is happening:
The engine is a 2006 Mercruiser 5.0L MPI. The engine starts fine, and idles fine. If they increase throttle everything works fine, and the boat can get on plane with no issues. Once off of plane, as they throttle down, the engine will stall. It fails as though there is a complete loss of power, that is, as if someone shut the engine off with the ignition key. This is very repeatable, and always seems to happen in the vicinity of 1500 RPM. It seems to run fine at 1400 RPM and below, and 1600 RPM and above.
There are no fault codes. The mechanic has checked out all of the sensors and they seem fine. He suspected the wiring harness and that there was an intermittent disconnect based on engine vibration at 1500 RPM, but a new harness did not fix the problem. Most of the electrical components (distr cap, rotor, cam sensor, spark plugs and wires) have been replaced.
Some recent history that may or may not be relevant: the engine overheated in 2015 due to clogged manifolds. After that the boat seemed to be sluggish getting on plane. In 2017, the engine had a severe loss of power (no ability to get on plane). This tuned out to be a partially melted crank position sensor that was attributed to the overheat condition 2 years prior. During the troubleshooting process it was discovered that the engine heads had warped and they were machined. After these repairs, the boat seemed to perform better than ever during a trip last February.
The mechanics have ruled out a whole lot of things besides what I mentioned above, so we are heading into checking some of the more expensive parts like the MPI computer. I am hoping someone has run into this and knows what the root cause is. Any advice or suggestions are appreciated. Thanks in advance.
Here is what is happening:
The engine is a 2006 Mercruiser 5.0L MPI. The engine starts fine, and idles fine. If they increase throttle everything works fine, and the boat can get on plane with no issues. Once off of plane, as they throttle down, the engine will stall. It fails as though there is a complete loss of power, that is, as if someone shut the engine off with the ignition key. This is very repeatable, and always seems to happen in the vicinity of 1500 RPM. It seems to run fine at 1400 RPM and below, and 1600 RPM and above.
There are no fault codes. The mechanic has checked out all of the sensors and they seem fine. He suspected the wiring harness and that there was an intermittent disconnect based on engine vibration at 1500 RPM, but a new harness did not fix the problem. Most of the electrical components (distr cap, rotor, cam sensor, spark plugs and wires) have been replaced.
Some recent history that may or may not be relevant: the engine overheated in 2015 due to clogged manifolds. After that the boat seemed to be sluggish getting on plane. In 2017, the engine had a severe loss of power (no ability to get on plane). This tuned out to be a partially melted crank position sensor that was attributed to the overheat condition 2 years prior. During the troubleshooting process it was discovered that the engine heads had warped and they were machined. After these repairs, the boat seemed to perform better than ever during a trip last February.
The mechanics have ruled out a whole lot of things besides what I mentioned above, so we are heading into checking some of the more expensive parts like the MPI computer. I am hoping someone has run into this and knows what the root cause is. Any advice or suggestions are appreciated. Thanks in advance.
