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56 evinrude 15 piston boss slop

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phil_l

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"Guys,
I had a question reg

"Guys,
I had a question reguarding slop between the rod/wristpin and piston boss for a 56 evinrude 15...model 15016. Currently I have two torn down doing complete rebuilds on them. My question is when you hold the rod in one hand and move the piston against the wristpin there is a small amount of play between the piston boss and wristpin. What I mean is a small amount of side to side play. If you try to press the pistion back and forth against the rod there is no play whatsoever. These pistons bosses have roller bearings the wristpin sits on. All my experience with other type motors and pressed wristpins is that if there is slop the piston/boss/wristpin/rod is bad. I couldnt find any information in the Seloc manual about this or even any mic specs for the piston boss or wristpin.

I havent yet pressed the wristpins out, which I will be doing next to inspect the bosses, wristpins and bearings. This occurs in all four pistons from both powerheads so I am thinking it is normal for these pistons or by some unlucky stroke I have four bad pistons....

Anyone have any info if this is acceptable/normal? Or have mic specs and tolerances for the bosses/wristpins?

Thanks for the help...

Phil L"
 
"Phil.... If what you're s

"Phil.... If what you're saying is........

Consider having the piston and rod assembly laying on a work bench in the identical horizontal position as if it were actually in the engine. There is absolutely no play when pushing the connecting rod into or pulling it out the piston BUT there IS a slight bit of play when the connecting rod is lifted straight upwards.

If this is the case, it's been my experience that this is a normal condition UNLESS the connecting rod can be moved at an angle (wobble) which would indicate a offset worn condition of a wrist pin, bearing, bushing, piston.

In actual operating conditions, the connecting rod to crankshaft alignment keeps that rod centered and prevents the connecting rod from moving off center at the wrist pin."
 
"Joe,
Thank you for such a

"Joe,
Thank you for such a quick reply. I will recheck under the conditions you speak of....

If there is a slight wobble indicating wear...I am assuming I would have to replace pistons bearing cage/needles and wristpin....Are there any micrometer specifications for the bearing surface of the rod itself to check for wear there, other than obivious out of round?


Phil L"
 
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