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Engine cylinder boring

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lotofquestions

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I acquired a 2015 4 cylinder 4 stroke 200HP Yamaha outboard engine. The YDS data shows it overheated about 26 times in its short 31 hour life. The over heat was caused by the water pump impellor melted into tiny pieces and got pump up into the power head. I disassembled things and removed all traces of the old impellor. So the overheat cause is solved. The engine now starts, cools as it should, and runs smooth except for the sound of piston slap at idle. Compression is 140, 130, 120, 160 . Quick and dirty leak down test indicates compression leak is from the rings.
Looking at the block with the head removed, cylinder bores are smooth with no scratch's, but they all measure oval shape. Wider in the horizontal plane. My question is, can this modern motor be bored out. I did find WSM offers oversize pistons for the task. I read that Yamaha uses some kind of spray on sleave. I could use some advice on how to proceed.
 
Yamaha uses flame sprayed cylinder wall liners in some models but not in your I4 F200 model. Even those blocks can be reworked if a repair shop has flame spray capability.

If you can find oversized pistons and rings there is no reason that it can not be bored oversize, providing it is within Yamaha specifications. Even then, you might be able to go a fraction of a millimeter over.
 
Boscoe Thank you. I was hoping that was the case. From what I can tell Yamaha only offers a Standard size piston. Looks like WSM has options up to .030 over.
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