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spark plug electrode broke off into cylinder#8 2005 VLX monsoon 340 500 hours


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I just found out i had an electrode break off into my cylinder, it had been running rough for a while now and i was finally able to get it to my mechanic who explained what happened. The boat didnt smoke or anything, just ran rough particularly at idle.

Trying to decide on options. New long block?

try to sell as is?  (I also have a full set of skins not yet installed from Gabes, existing skins are still fine so i was waiting to install the new ones)

Rebuild existing? 

What do you think the cost to re-power with a new long block would be.  I would not attempt to do it myself. i know my way around chevy engines but i would hire it out.

Maybe just pull the head and see what the damage is? 

no compression on #8 so stuck valve?

Pretty frustrating. 

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4 hours ago, Javabean said:

Maybe just pull the head and see what the damage is? 

Rather than speculate, it is easy enough to remove the head and take a look.

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3 hours ago, justgary said:

Rather than speculate, it is easy enough to remove the head and take a look.

Yup.  Easy enough to do in the boat.  Alternately get a scope and look down the plug hole .  I'd be leaning towards hole in piston.  Stuck valve would be easy enough to see by removing valve cover.

Edited by oldjeep
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Surf4FamFun
21 minutes ago, ROFF said:

Borescope it.    Should be able to see everything.   

Ditto, if it is a valve(s) your would still want to know how the top off the piston looks.  Have not used a bore scope in a very long time, modern version probably would let you see scoring I the cylinder wall I would think.  

I think hours would factor into the decision.  If you the first owner, good service history, are at 800 hours and it was strong before with even compression on the other 7 holes a head service and go with a bent valve probably makes sense.  If you are at 2,100 hours, two oil changes, and bad compression on a weak engine options would be more expensive.  

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