Cause of 15 hp mercury powerhead failure?

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sep

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Oct 1, 2003
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I bought a 15 hp Mercury short shaft brand new in 96'. Last night the engine seized up requiring a 20+ mile 7 1/2 hour float down one of the local rivers.<br /><br />I took it in to a shop today and the mechanic poked and prodded and determined it either threw a rod or a ring(s) went bad. <br /><br />What are the most likley causes for this type of failure? Will sustained running at WOT cause this? Is this typical of two strokes? I treated this engine well from day one and always mixed the gas as appropriate so I don't believe it to be a lubrication problem. <br />Any info provided will be greatly appreciated, Thanks <br /><br />Sep
 
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ZmOz

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Aug 13, 2003
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Re: Cause of 15 hp mercury powerhead failure?

Did you decarb regularly? It could have overheated for one reason or another. Sometimes motors throw rods with no real reason behind it. (possibly a small defect in the rod during manufacturing)
 
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sep

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Oct 1, 2003
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Re: Cause of 15 hp mercury powerhead failure?

A little more background info may be in order. I had less than 200 hours on it and there was water on the top spark plug when we removed it. I regularly brought it in for service as required in the manual. After each trip out, I would disconnect the fuel line and let it idle til it ran out of fuel...just like the owner's manual recommends. Could an excessive amount of water in the gas have caused the problem?
 
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phatmanmike

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Oct 24, 2003
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Re: Cause of 15 hp mercury powerhead failure?

if there is water on the plug, that means there is water in the cylinder. if there is water in the cylinder, that means there is water on the bearings, and water on the bearing is a no no. water, in any amount, is too much. find the cause of that water and there's your reason rite there
 
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