Not just for ODDD1, but he seems to be ignition guru on this forum.<br /><br />A couple of week ago I posted this about a 2000 Merc 90:<br /><br />"Would a faulty CDM be consistent with this:<br />Sometimes, but not always, slow out of the hole.<br />When OK from the hole, runs great and full 5000 rpm for about 1000 yds then drops back to 3800. Sounds as if its running fine - just won't give more than 3800. Also, changed all 3 plugs, did not help. All 3 plugs always wet."<br /><br />I ran boat like this maybe an hour or so a day for perhaps 5 or 6 days over a two week period after putting in new plugs.<br /><br />I took a good look at plugs today. Top plug looks different from other two;<br /><br />Top: center electrode is black, white middle part is very white with a small black “smile” at the outer edge. <br /><br />Other two: center electrode is silver or gray, white center is slightly off white with no “smile”<br /><br />Also, looking at the top of the cylinder, Top is noticeably cleaner than bottom two.<br /><br />Also, I had changed all plugs and got no improvement. Cleaned off old plugs and one of them had black center electrode, others were gray. Have lost tract of which one was top.<br /><br />Can anyone tell me if I have one bad cylinder or two?<br />CDM or something else?<br /><br />As problem SEEMS only at high end, would checking for spark in my driveway tell me anything?
