Problems
 

Could be, did you shoot a deer?

Could be one of several hundred possibilities. Sucked something into the middle carb and it digested through the middle cylinder, Broke a reed and it closed the plug gap, broke a ring and it closed the gap, the keeper may have fallen out of the piston and the ring turned causing an end to snag a port, the list goes on and on. Only way to tell is to pull the head and start an autopsy. If it closed the gap on the plug, it ain't gonna be cheap. It's just to see how much damage to which parts. Could need a re-sleeve, could be a simple bore job.
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Thanks I'm hoping it's just that 1 cylinder the motor has 300hrs top. CajunChristian I'll be in touch.

Nope didn't see one! Broke motor and no meat!

Could be water!! (Head gasket or in the water intake up on the side) Don't wait to tear it down, had a buddy with a 90 that happened too on the bottom cylinder, it's locked up now and has already been boarded, so it's either sleaving ( very expensive) or find a new one/ New used one.

in March I'll have owned it for 3 years it had 100hr or less I sure hope I can get it fixed for under 1500, don't really want to justify spending that extra money!

I have motors re-sleeved for right at $250 per hole.
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Sorry I didn't get a chance to call you. We are going to pull it apart tomorrow and see what she looks like I have a couple pics of #2 plug something broke that wasn't supposed to. Attachment 62687Attachment 62688

Time for that 70

That'd be sweet but I am not ready to get off that money yet!

I would bet your piston came off the rod on that cylinder.

pull all 4 plugs then stick a screwdriver in the #2 plug hole and turn the flywheel by hand and feel if the piston goes up and down as it should. if its disconnected it wont go down on its own.

a knocking sound is almost always going to be piston or piston rod related.

looking inside the plug hole you might be able to see if there is something on top of the piston but if that were it most likely would jam the piston and seize the motor.

I don't think its going to be a minor problem, that said it may not be too much of an expensive fix if the cylinder wasn't damaged.

Matt, please don't make the same mistake most rookies make, they repair the problem and never find the cause. If you simply repair the problem, it usually returns to cost you again. Every failure has a cause, find the cause, then fix the problem:)
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Great advice

Everything he describes are symptoms. The closed plug gap. I bet when you pull the head, it is pock marked also, another symptom. Something beat around in that cylinder. I sure hope it didn't break a piece of the sleeve of where the ports are.
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is it insured? instead of posting about it on here, u should of sank the boat and let insurance get u a new one. too late now. lol

Sorry, but that would be insurance fraud:(
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No insurance lol. It's been frozen here since I'm dragging it over to my buddies but I do agree something caused it to fail just have to find out what.

X2

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I agree also..... Always good to live by the square.

Attachment 63232here she is blown #2 getting her bored tomorrow crank was good. They'll be looking for the root of the problem tomorrow also.

Awww...that's just a flesh wound. Hit her with a few passes from a flat bastard file, a new set of rings and she'll be good as new;). You are lucky the piston didn't seize in the bore and bend a rod and crank or bust out the block. Good luck on the repair.

Ijust talked to repair shop #1 &#3 just honed and #2 .020" over bottom bearing on crank was busted but all in all it's better than I expected, by Monday or Tuesday of next week I should be in break in mode!:D:D

What was the cause?

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Carb to lean cause ring to fail on exhust side.

That is a symptom, not the root cause of the problem. What caused the carb to suddenly lean out? Not being a a$$, just trying to help you solve your problem. Unless you solve the problem, the symptoms will reoccur.
Danny

My mechanic is looking into oil system. I'm thinking I'm going to pull oil injection off and mix fuel. It may have had something to do with the freezing conditions but the wear that was there was brand new do he seems to think its something that failed all of a sudden and not over a period of usage. And I take all you guys comments seriously I appreciate you helping me Danny.

I have a Mega in my shop that looks exactly like your Yammie. Middle cylinder has aluminum galled on the walls over the exhaust port. This motor was operated in 5 degree weather with a frozen water system, it overheated. The plugs and the piston you show do not indicate a lean condition. A lean condition would turn the plug white and leave zero carbon on the piston. Usually a lean condition will gall aluminum on the intake side first. Overheating will gall aluminum from the exhaust side first since it is the hottest place in the cylinder.
The factory jets carbs for all conditions from 0-120 degrees, that's why most factory motors run pig rich. Carbs don't just suddenly lean out. Especially if it was running great just before it died. My guess would be overheating, frozen water pump impeller????? I would drop the lower unit and check the impeller. It may have been frozen and sheared the rubber impeller from the plastic hub. It will look normal, but try to spin the rubber portion while holding the driveshaft, if the rubber turns, change it out.
As for removing the oil injection GREAT IDEA. A pinhole in an oil line and you grenade a motor. Hand mixing is a 100% fix for that problem.
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Frozen water did cross my mind a few times.

I really don't see a lean problem there. Frozen water system on your motor. You have most likely found the cause. Next time it gets cold, drain the motor's water system when you put the boat on the trailer:)
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I have seen 40hp Mercs do this. The water pump impeller would spin on the hub. At idle and low speeds, it would pump great. At anything above 2500 rpm, no water. That was a factory defect in the impellers. Yours sounds like a frozen impeller due to low temps.
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could be, I was out hunting Friday before last in all that sleet and freezing rain, Saturday I was back everything still frozen over let motor warm up a couple minutes then left but that afternoon on my way back motor sputtered on take off but I thought ole 2 stroke cough... Sunday I didn't make a mile and poof. Mechanic said whatever it is wasn't something pre existing it's something that had just happened, I just called and said change water pump also, being that these guys are only charging me parts at cost no labor I may as well.

Not that I am the all knowing guru of 2 strokes, but my diagnoses would be overheating which is also a symptom-not a cause, now you need to find the cause of overheating, check water pump. Certainly not a lean problem, no evidence points to lean burn. All evidence points to overheat.
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Water pump on order, it may even be riginal pump in there so just change as precaution. Again thanks much for your suggestions!

You are most welcomed. Just trying to help:)
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Danny you the man!

Matt where do you find free labor? We've all needed that a time or two.

Life long friend offered it.

Picking her up today had to bore .020" over on #2 and had #1&3 honed, went new with everything except crank and powerhead. I'll be putting some break in hours this weekend!

Glad to hear it's lined out!

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