Problem: The motor shows 125 top - 30 Middle and 125 Bottom. What had happened beofre the compression drop was: After the motor runs for 5-10 at max power is good and warmed up , it totally dies (as if I pulled the deadmans switch). I throttle down and re-start it usually runs fine and after a few minutes at high rpm it dies again. If I restart it and then keep the rpms to 2000 it continues to run. I took it out and tried out my newly rebuilt lower unit and it failed again after running it hard for 5-10. It was harder to start as if there was some internal resistance. It did restart and died at higher rpms. I restarted it (this time it needed more throttle to get it started) I got it going and kept it to 2000 and limped to shore under power. It now seems to have a rattling/pinging sound and vibrates/shakes as well which it didnt do before. As if it were having pre-ignition/detonation problems.<br /><br />Background: This motor had been kept up. It had compression of 125-125-126. I rebuilt the fuel pump with a Merc kit about 3 years ago, always use Quicksilver oil and regular gas Octane probably 87 I dont use high test just the cheaper regular grade, have installed an inline gas fuel filter in my inboard tank, decarbonize my engine with Merc/OMC engine tuner each year, add a Merc fuel cleaner additive with most fill ups, annually change spark plugs, lube all fittings, installed a new impeller 3 years ago and lower unit fluids each year/ or twice a year. I do all maintenance Merc recommends each year except carb tune ups or adjust timing (that has not been done for at least 4 years). It has been running fine (sometimes a little sluggish out of the hole but not bad) so I just keep it oiled and lubed with Merc products and it has served me well. <br /><br />Symptoms:<br />July 26th was the first time I noticed any problem of any kind with this motor it was on our 2 week fishing trip in Canada. It may been just coincidental that it noticed a problem - when I switched from the inboard tank to a 6 gallon auxillary tank with a separate line. I had been running 5-10 at max power and it suddenly surged and then just died. I noticed that I had not vented the aux tank (opening the air vent lid). I realized it and vented the lid, restarted it and ran hard for 2-5 and it died again at full power. I then switched back to the inboard tank and ran it only at 3000-4000 rpm and it seemed to be operate fine it made a very slight rattling sound. I checked the pressure in the fuel bulb and it seemed fine. I then checked the motor over, put new NGK plugs in it, put new gas in the tanks and operated off the inboard tank. I checked the motor over for a loose carb or loose parts and everything looked good, I checked the fuel lines and vent which seemed okay. I went out and ran it full power for 2-5 and it died suddenly again. I restarted it and operated it at 3000-4000 rpm and it ran fine. I installed a new (white cylindrical Merc) fuel filter under the cowling. I ran it off the inboard tank and it failed again but after 5-10 at max power. I restarted it and ran it 3000-4000 and it continued to run just fine. I continued to operate it like this for about 6 days in Canada. <br /><br />During that week I re-designed my lower unit on a rock which I had rebuilt by a reputable Merc dealer. When it was being rebuilt I drained the gas from the line that hooks into the attachment at the front of my motor and didnt not see any water, sand or debris from the drained fuel. I let it air out well.<br /><br />When I installed the lower unit and went to test it out. The motor was sounding fine and working fine in all aspects (shifting was good, good water flow, water from pump was running fairly cool, no unusual sounds (it had a slight rattle but in the normal range),ran smooth, etc). I took several 5 10 runs and it seemed to be fine. I then took a high speed run 5-10 at max power and the engine died totally. I went to restart it (in N at the start position on the throttle) and it turned over hard even though I had charged up the (1 yr old) battery the night before and it was run hard and I believe the alternator is fine it had always been able to keep the batteries in good shape. It started okay and I ran it up to 4000-5000 rpm and after 2-3 it died again. I repeated this pattern a few times. Then I decided It was time to limp to shore. I started it up (it needed a higher throttle setting to start) and kept the rpms at 2000 or less and was able to keep it running and get to shore. I had pumped the fuel bulb and it seemed like it had plenty of gas and pressure in it. I did not need to keep the bulb pumped so I stopped doing that and at 2000 or lower it would keep running. When I got to shore it was running really rough and had a rattle/pinging/like a tappet sound in a car. It did continue to run at slow idle. I check the cylinders and the top one was hotter than the bottom 2 by quite some amount. They were all fine - none were too hot to touch the top cylinder was considerably hotter than the other 2. I checked the spark plugs for spark and each has spark when I cranked it in a cold start. <br /><br />I am wondering how the middle cylinder could have become scored and lose compression and what I could have done to have prevented this. Are these 60 hp Merc's solid or is this a common occurence? I have a good friend who has this same motor and I don't want him to go through this as well. Any suggsstions? 