I just had my first merc problem ever, now on my 3rd 2 stroke merc (1st was a 1987 20HP, 2nd 1992 150 XR6, 3rd 2004 50 ELPT)! At any rate my first problem was an electrical issue, the tach stopped working. No big deal, power pack, loose wire, stator, or something. The motor kept running and I kept using it (might have been a bad idea) and the 5th time out, on the way back to the ramp the motor acted like it lost a cylinder and died!

I popped the cowling off, noticed a melted wire bundle (harness) between the rectifier and some other electical components. Tried to start the motor again, got it running ok (tach working and everything), but shut it down so the engine wouldn't catch fire or soemthing real bad. Used the trolling motor to get back to the ramp and loaded the boat.

Being pressed for time and not wanting a long drawn out repair process I decided to take it to a repair shop. The shop guy told me he bypassed the stator and rectifier and has the boat running. He will order a new stator and rectifier as the old ones are shot, and can install (approx $500 total). Not a big deal saved me the time and would have some warranty, I said go for it.

Parts arrive at shop and are installed and the shop guy tells me the motor started right up, ran rough, then stopped working altogether. After several tests he noticed he lost all spark so he will try to test coils next day. In the meantime the shop decided to try a compression test and found top cylinder 110, middle cylinder 60, and bottom cylinder 110! That was not good news!

I was wondering if using the boat with a bad rectifyier/stator would have shut down any oil sending equipment or warning equipment as it is an oil injected 2 stroke with the oil tank under the cowling. When I looked at the oil level in the engine it looked like it had been sipping oil for the last quater of a tank (5gallons) but it wouldnt have needed that much. I am confident the shop will have some answers, I am just not sure they are what I want to hear. If you all would be so kind as to speak your mind/opinion on some potential problems and cures I would be very greatful.

What other problems could I expect (burned cylinder, blown block, head gasket)? What are some options that I have for repairs or items that might have been damaged so I have an idea when the shop gets back in touch with me?

It's hard to say without seeing what was damaged from wires melting. They may be able to tell you if it due to lack of oil that caused failure.

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After speaking with the mechanic, still not sure what caused the wire meltdown or the bad compression in middle cylinder, but the electrical problem seems to have been resolved with a new stator and rectifier. My father was able to track down another message board that had a similar situation with the same motor -- http://forums.iboats.com/showthread.php?t=133622
seems that poster had a wire meltdown, but no compression loss afterwards! I am sure that the electrical gremlins have been silenced (at least for now), so its on to a larger problem.

The situation now seems to be more focused on the low compression on the middle cylinder (I am not sure that I stated before that it was a 3 cylinder). The mechanic has been speaking with Mercury over the phone regarding this issue and he said that Mercury would replace the powerhead for free and he would just charge labor to install. I asked how he knew that the powerhead was bad (ie what tests had he performed) and his reply was since it was the middle cylinder, that was for sure the culprit - a bad powerhead. That plus the Mercury customer claims people were so readily willing to replace the powerhead even though the engine has been out of warranty for just about a year. Something like they want to keep people happy and that this might be a reoccurring problem. Seems kind of odd to me, but I wanted to pass this one by everybody before going any farther.

Hearing this news I am inclined to head over to the mechanics and remove the head to see what has gone on. I have heard that I will see damage to the head gasket or the cylinder walls. The explanation for possiblity of head gasket damage is that a bad detonation (bad electrical) could have caused the cylinder not to compress the fluid and the path of least resistance would have been the head gasket or maybe a ring. The carberator is another place I would like to look at for the possibility of finding a reed valve issue.

What do you think? Are there any tests for diagnosing powerhead issues? I keep hearing about leakdown tests, but not sure what or how that is done. Last year I was on a 40HP Yamaha that blew the head gasket and there was a bunch of steam comming off the motor, I am sure from the cylinder and the block, so that might not be my problem either as I never saw that heppening in my case. I know that pulling the head is fairly easy and think that should be done to ensure the powerhead is shot before going ahead. On the other hand, I dont want to get in the way or obstruct a somewhat free powerhead replacement. I am really at a loss and would really apprectiate your advice.