Hello. I have a Mercury 850 that is causing me to actually lose sleep stemming from my frustration. Two years ago I acquired this engine and found it to have a damaged piston/cylinder. Eager to get it going again, I sent the block off to a reputable shop in FL to have it overhauled which came back in great shape. While it was being repaired, I replaced, with new parts, almost everything else associated with the engine - new plugs, wire set, water pump, CDI control box, starter solenoid, battery, timing belt, fuel lines, fuel pump (overhaul), fuel tanks, and carb kit overhaul. I think that, if it can be replacedor overhauled, I've done it (with the exception of the wiring harnesses).
After doing all of this and reattaching everything, the boat fired right up and ran like a beast all last season. I ran the recommended 25:1 ratio of fuel/oil for the first 10 operating hours to break in the new block. Around Sept/Oct, I noticed that the engine began having problems starting when it was cold, then the problem rapidly escalated into having issues starting even when the engine was warm. Finally, the engine just died while it was running and it was nearly impossible to get started - wouldn't even fire, then choke and die. Appeared almost to have no combustion abilities at all.
So I parked it in a garage (did not do a winterize on it) and just pulled it out about a month ago. Of course, remembering the issues I had with the engine in the fall I decided to give 'er another try. Had some issues getting it started but it did eventually come around and fire - ran very poorly. I dropped it in the lake to complete the fuel/air mixture adjustments and it ran as long as I kept the warm up lever all the way up - in fact, I was actually having to adjust the speed of the boat using the warm up lever and not the throttle arm. This was the only way I could keep the engine alive. Once I ran it for about 20 minutes, I voluntarily shut 'er down and it never again came back to life. It would just turn over, showing little interest in even trying to run. My initial thought was that the carbs and plugs were fouled from the 25:1 mixture I ran through it last season.
So I bought and replaced all plugs and bought another 2 carb overhaul kits. Then I checked the fire from each spark plug (plug to ground on engine) and I have great fire from all four. Figuring I still had a carb problem, I again overhauled the carbs and checked every single passage way - with nothing showing as problematic. Both carbs were clean as a whistle. I put all new gaskets on them and reassembled. Still nothing. It turns over great but I just can't get any life at all. I'm doubtful about a compression problem (since it is newly-overhauled and there wasn't some kind of dramatic loss of power or terrible noise when problems began to surface last year), the fire is awesome and there is no evidence of a carb problem. I've never tampered with the adjustments on the distributor and am fearful to do so - don't want to get in over my head, but I'm at a loss without continually thinking the ignition timing has somehow "gotten off". Does this happen? Could something have worked loose to cause this?
I'm checking compression this evening and expect that the compression will be fine. What else is left, if compression is fine? Am I missing something critical? How could this engine be so sick that it won't fire for even a short time? Is nature getting back at me for something I've done by suspending the laws of physics just in the case of this engine?
Any help would be GREATLY appreciated!!!!!!
After doing all of this and reattaching everything, the boat fired right up and ran like a beast all last season. I ran the recommended 25:1 ratio of fuel/oil for the first 10 operating hours to break in the new block. Around Sept/Oct, I noticed that the engine began having problems starting when it was cold, then the problem rapidly escalated into having issues starting even when the engine was warm. Finally, the engine just died while it was running and it was nearly impossible to get started - wouldn't even fire, then choke and die. Appeared almost to have no combustion abilities at all.
So I parked it in a garage (did not do a winterize on it) and just pulled it out about a month ago. Of course, remembering the issues I had with the engine in the fall I decided to give 'er another try. Had some issues getting it started but it did eventually come around and fire - ran very poorly. I dropped it in the lake to complete the fuel/air mixture adjustments and it ran as long as I kept the warm up lever all the way up - in fact, I was actually having to adjust the speed of the boat using the warm up lever and not the throttle arm. This was the only way I could keep the engine alive. Once I ran it for about 20 minutes, I voluntarily shut 'er down and it never again came back to life. It would just turn over, showing little interest in even trying to run. My initial thought was that the carbs and plugs were fouled from the 25:1 mixture I ran through it last season.
So I bought and replaced all plugs and bought another 2 carb overhaul kits. Then I checked the fire from each spark plug (plug to ground on engine) and I have great fire from all four. Figuring I still had a carb problem, I again overhauled the carbs and checked every single passage way - with nothing showing as problematic. Both carbs were clean as a whistle. I put all new gaskets on them and reassembled. Still nothing. It turns over great but I just can't get any life at all. I'm doubtful about a compression problem (since it is newly-overhauled and there wasn't some kind of dramatic loss of power or terrible noise when problems began to surface last year), the fire is awesome and there is no evidence of a carb problem. I've never tampered with the adjustments on the distributor and am fearful to do so - don't want to get in over my head, but I'm at a loss without continually thinking the ignition timing has somehow "gotten off". Does this happen? Could something have worked loose to cause this?
I'm checking compression this evening and expect that the compression will be fine. What else is left, if compression is fine? Am I missing something critical? How could this engine be so sick that it won't fire for even a short time? Is nature getting back at me for something I've done by suspending the laws of physics just in the case of this engine?
Any help would be GREATLY appreciated!!!!!!
