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OK, well it looks like the piston coked up, causing the stuck rings, leading to the melt down… The rings look properly aligned, so I don’t thing the alignment pin for the top set of rings came out…
Perhaps they were using crappy oil…
Hone the cylinder, then remeasure…It won’t be perfect, but will work just fine I’m sure…Don’t “over hone” it to get rid of all the little score marks, use a ball hone to finish up, it will get rid of any little problems and chamfer the ports.
Again, it depends on how perfect you want it…Another possibility I didn’t consider regarding the piston coking up.
Would the theory be that the rings stuck, then hot compression gasses
got past the rings, over heating the piston?It must have been making a hell of a rattle before the last guy shut it off!
Thanks all, for the thoughts and suggestions.A couple of ways to think about this…..Once the piston is “coked up”, it loses some ability to dissipate heat…Creating a bit of an overheat situation that led to the scuffing…But, it surely is possible that once the rings stuck, the blow by created more heat on that area of the piston also…
Frank’s ring locating pin theory makes sense, I made my judgement based on the fact that the rings still looked properly aligned, but that nasty cavity in the piston dome may have been from the ring locating pin migrating out…Guess we will find out when he yanks the rings off that piston…
In any event, it seems like both pistons should be replaced with the beefier locating pins…
Do the original rings supercede to the newer style, it would seem like they would…You just couldn’t use the original style rings on the newer pistons….OK, answered my question by rereading the bulletin…
Just looked up the pistons for the 59 35hp (marinengine.com), I don’t see any number changes for the pistons…Do the improved pistons have the same part number??Look closely and you will see something truly amazing. The loose dowel beat its way all the way up through the piston crown as the piston reciprocated back and forth. It also beat its way downward and broke the second ring. That thing ran a long time with the damage. OMC tough.
So Frank is saying that the ring pin beat a hole upward into the piston dome, then found its way back down that hole beating another hole down inside the piston to the second ring? Wonder if the pin is still in there somewhere?..
Would love to see a picture of this piston after the rings are removed, perhaps media blasted so the path of the pin can be seen….Pretty respectful of that pin not to chew up the cylinder wall…So Frank is saying that the ring pin beat a hole upward into the piston dome, then found its way back down that hole beating another hole down inside the piston to the second ring? Wonder if the pin is still in there somewhere?..
Would love to see a picture of this piston after the rings are removed, perhaps media blasted so the path of the pin can be seen….Pretty respectful of that pin not to chew up the cylinder wall…What I’m saying is that at 5000 RPM, the piston is making 10,000 strokes a minute, 5000 up and 5000 down, or 167 strokes a second. That loose pin was like an ice cube in a cocktail shaker, beating back and forth at an incredible rate. I wonder how many G’s that is? Till it finally broke out the top and out the exhaust ports. On the encouraging side, there are an awful lot of motors out there that haven’t failed.
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