rebuild question

rockyrude

Lieutenant Junior Grade
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Sep 10, 2007
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1,120
I've got a 1978 140hp that has a scored cylinder from being over carboned (if that's even a word). While I'm waiting to find out the piston size, it seems to be o.k. to do just one cylinder. My question is do you guys replace the rod also or re-use it with the new piston?
 

wilde1j

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Apr 15, 2002
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5,964
Re: rebuild question

The rod may be reused if it's OK. You will need to mic it's ID with an inside micrometer all around to know and don't forget to very carefully inspect the roller bearings. It's OK to do only one hole, BUT you need to establish and correct why it failed (or it most certainly will happen again. Did carbon cause a ring to break? Heavy carbon is often caused by an excessively rich mixture in the failed hole (typically an induction or carb problem).
 

emdsapmgr

Supreme Mariner
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Dec 9, 2005
Messages
11,551
Re: rebuild question

I also reuse them. Note that during reassembly to the piston that there is an "up" side to the rod, based on the oil hole. These crossflow engines typically suffer from carbon issues with age. OMC recommended annual decarb use of their Engine Tuner product for that reason. Also, make sure the engine is running at normal operating temps-engines which run cold (stuck open stats) will tend to accumulate carbon on the pistons/rings quicker. I'd re-ring the other 3 pistons and hone the cyls prior to reassembly.
 

rockyrude

Lieutenant Junior Grade
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Sep 10, 2007
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1,120
Re: rebuild question

I had planned on reringing the other three, if one broke the odds are the other three could be questionable. Since I have more experience with cars than outboards, do you guys use assembly lube on reassembly?
 

wilde1j

Vice Admiral
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Apr 15, 2002
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5,964
Re: rebuild question

Yes, ATF and heavy grease on the needles to hold them in place.
 
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