Am i in to deep

so i have a 95 johnson 115, model j115tleor. the piston ring failed and totally destroyed my piston, head and cylinder wall, well not so bad on the cylinder wall. i suspect the failure was caused by loss of spark. i have undertaken the rebuild as a DIY project cause of the insane repair costs i was quoted. currently i have it striped to just the block, crankcase, intake and exhaust manifold. i am ready to lift the enigne and put in on a bench to strip the rest of the way. i have everything labled, i mean every bolt every wire ever nut and all bolts are in baggies and sealed. and im pretty confident in my skills although this is my first outboard repair of anykind. i have the manual and i am a engineering electrician so tech manuals, drawings and schematics are part of my everyday life. so when i say this is my first outboard repair i mean my first, never even changed a sparkplug on a outboard. am i in to deep on this, any advice before i go breaking open the crankcase and pulling pistons out. i do plan on boring all cylinders just cause it would be stupid not to. i feel confident but who knows what i might encounter. thanks for any advice.

Re: Am i in to deep

You need to accurately diagnose and treat the original problem or you'll be back doing it again in short order. No spark is not a very likely culprit for a ring failure. Diagnose first before tearing it down any further.

Re: Am i in to deep

what are some common ring failure cause's? loss of oil. if its an internal problem i cant determine the cause without tearing it down. everything so far has looked good, carbs are clean and easy to move, flywheel looks great. i looked in the intake with a flash light and looks clean free of carbon build up. so loss of spark is my only suspect at this moment.

Re: Am i in to deep

Ring or piston failure is generally caused by detonation or over advanced spark. Sometimes even too hot of a spark plug can set it off. Lack of spark in a two stroke engine gets a wet oil fouled spark plug and carbon build up in the exhaust system of the engine, not piston failure. An engine which is run at very high rpm for long periods will sometimes suffer from ring breakage but usually only on an engine which is worn out and has play in the ring grooves of the pistons. Hope this gives you some where to begin looking. Go for the overhaul, but inspect everything, carbs which look clean could have a tiny piece of trash partially colgging a jet and causing a lean mixture on one cylinder. That could easily be your problem.

Re: Am i in to deep

Rings also fail if they coke (carbon) up too much, have no room to float in the groves and catch on an exhaust port. This can be caused by running the motor too cold - t-stat stuck open or the like. Or, by simply neglecting to decarb on a scheduled maintenance cycle. Take a look at the piston that failed through the bypass cover and the combustion chamber. Is it excessively carboned up?

Re: Am i in to deep

ive taken the cylinder heads off and all the pistons are black and pretty rough. i do suspect neglect as far as maintanence and decarboning goes. im not the first owner so i can only guess. but so far everything else looks good, so im suspecting maintenance neglect and loss of spark are the cause unless something else comes up during the strip down. one ? whats the best way to clean carbs, i am going to get a reuild kit for them but as far as i can tell that only takes care of the gaskets and o-rings.
thanks

Re: Am i in to deep

To clean carbs, I disassemble them and soak them in a bucket of carb cleaner for a couple of hours. Then I blow all the passages out with compressed air and aerosol carb cleaner. Then I run a fine stranded wire through all of the passages I can get to, blow them out again, and reassemble.

Re: Am i in to deep

Excessive carbon in the combustion chamber isn't caused by no spark.

Take a careful look at the ring grooves and see if they're full of carbon. If so, there's your direct cause for the ring breaking. If your plugs look black or sooty too then maybe this motor was running too rich, or had the wrong plugs. If so, you should think hard about replacing the jets in the carbs when you rebuild. They could be the wrong size or have been damaged during cleaning and are oversized.