Originally Posted by Mark rsa2au
I pulled the correct temp sensor out (with the 2 wires) and tested resistance at 10deg C intervals up to 90degC and it was fine. A few ohms out from spec or the thermometer I was using was a little out, but either way it was registering HOT.
Engine was in Diagnostic mode at 1000rpm. How do I check the shaft bush, which shaft? the distributer shaft I assume?
Cap rotor and plug wires are origional - 270 hrs on a 2001 boat
Can you run it at night or in total darkness? Your plug wires are old. The fact that they "only" have 270 hours is immaterial, they age, even though they're silicone. One thing that happens is, if the engine has been run hard at all, the conductor eventually loses conductivity at high frequencies, which means it may measure good with a multi-meter, but run like crap. A meter checks for DC resistance, but spark isn't DC voltage.
If you do run it in darkness, you may see arcing between the wires and this is likely to be part of the problem. Could be ALL of the problem. Caps can also develop carbon traces and if this happens, it may not be visible, but it has a bad effect on how the engine runs. It will be inside, not outside of the cap.