Originally Posted by Mark rsa2au
Contacts on the inside of the Distributer cap are corroded. I have sanded then back a little to remove this but there is still some surface pitting. Looks like the best option is to get a new one and new leads as well. I agree this might solve the misfire.
Do you think will solve the running rich? I have been researching injectors and cannot find out what mine are. No colour coding and the numbers on top do not come up with any search. What if the fuel pressure regulator was messed with previously? Should I unscrew the adjuster to lower some pressure in the injectors? Or would a pressure gauge show this up at the shrader valve?
Never mess with a factory-adjusted part. That's set under controlled conditions, which we don't have. If the pressure is too low, the fuel won't atomize as well as it should and that means some cylinders will get more than enough, some the right amount and some won't get enough. Running hard and having some cylinders too lean will burn the valves and probably the piston, possibly scoring the cylinder(s). There's no way to "un-mess with" the regulator. If you think/know it was messed with, replace it. Also, leave the idle stop alone. This isn't like a carb- there's really nothing to adjust in the field. If you have correct compression, spark timing/intensity and fuel/air delivery, a sensor problem is the next most likely problem. Since you have replaced most of them, it's unlikely that you replaced a bad sensor with another bad one.
This doesn't leave many things to look at, but I did recommend measuring resistance from the sensors to the battery negatives and the ground at the back of the engine. If your ground is bad, it can run exactly as you described. It's too bad nobody in Australia has taken it upon themselves to buy the necessary diagnostic equipment for these, although I don't know how many ski and wakeboard boats are over there.