Tomco
Active Member
- Aug 16, 2012
- 455
- Boat Info
- 2004 420 Sedan Bridge
GHS Hydraulic Lift
11' Walker Bay, 30hp
- Engines
- Cummins 6CTA 8.3M
I'm looking at purchasing a 2001 Sundancer 340 with the 7.4MPI engines. The survey uncovered that the starboard engine was not putting out the same RPM as the port engine - 3900 vs. 4400. The current owner has been diligent (through a certified marine mechanic) but unsuccessful in resolving it.
Analysis so far:
* An orginal computer scan indicated the CO2 (I believe) sensor on the exhaust manifold was bad - this was replaced but made no difference.
* They found that the compression on one side of the engine was about 15 psi lower than the other side - they took the head off and did a magnaflux. A small crack was found and the head replaced - made no difference and there is still about 15 psi difference between the two sides.
* they have now found that the timing advances from 6 degrees to 16 degrees and will not advance any further. I understand that it is suppose to advance to around 23 degree at WOT. They believed it was a knock sensor (not sure if I spelled it correctly) - this was swapped with the port engine with no difference. The distributor and wiring has also been swapped between engines but has not changed the problem.
* They had a call with Mercury but that didn't seem to give them much to go on - they are now checking the resistance on each pin ... I have no idea what this means.
Just wondering if any of the tech savy members might have come across such a problem and have some guidance that I could pass on. As I mentioned above, this is not my boat (yet) but I will answer what ever questions I can. I do have a little engine background and can appreciate that this could be as simple as a loose wire or as complicated as flaky computer ... I'm also getting a bit uncomfortable whether to eventually close on the deal. I figure I can always make that call when its fixed and I know what the problem was.
Appreciate any thoughts ...
/Tom
Analysis so far:
* An orginal computer scan indicated the CO2 (I believe) sensor on the exhaust manifold was bad - this was replaced but made no difference.
* They found that the compression on one side of the engine was about 15 psi lower than the other side - they took the head off and did a magnaflux. A small crack was found and the head replaced - made no difference and there is still about 15 psi difference between the two sides.
* they have now found that the timing advances from 6 degrees to 16 degrees and will not advance any further. I understand that it is suppose to advance to around 23 degree at WOT. They believed it was a knock sensor (not sure if I spelled it correctly) - this was swapped with the port engine with no difference. The distributor and wiring has also been swapped between engines but has not changed the problem.
* They had a call with Mercury but that didn't seem to give them much to go on - they are now checking the resistance on each pin ... I have no idea what this means.
Just wondering if any of the tech savy members might have come across such a problem and have some guidance that I could pass on. As I mentioned above, this is not my boat (yet) but I will answer what ever questions I can. I do have a little engine background and can appreciate that this could be as simple as a loose wire or as complicated as flaky computer ... I'm also getting a bit uncomfortable whether to eventually close on the deal. I figure I can always make that call when its fixed and I know what the problem was.
Appreciate any thoughts ...
/Tom
