VP 5.0 GXi-G spark plug corrosion

stresspoint

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may be common on the 4.3, however nearly never happens on the 5.0 or 5.7
the few times when i have seen this happen on V8 Vortec motors .
(i have had my fingers on many a 5.7 and 5.0 motors ,FYI, i have a 5.7 Vortec ""i personally built"" that has close to 500 reliable and driveable hp in my toy boat :) ) .
i can tell you ,it does happen on V8s (not only Vortec ) as well you have just never seen it, where as i have.

each diagnostic , the gasket leak travels to the second bolt "in ", the water track goes from there down to the intake runner , not a lot but enough to cause intrusion.to the cylinder over time when the motor sits, each time it was apparent when the motor had a miss fire from start up after sitting . as Op describes.
the easiest way to determine if this could be the issue is to remove those 4 inner bolts starting with the 2 toward the front of the motor and check for sign rust ,
guessing as i am no xsput on all matters ,no rust on the bolts would mean that OP needs to start looking elsewhere.
either way its going to be head off to resolve this problem .
 
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Lou C

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Agreed I'd be pulling the manifold, and looking inside. The boat does not look like it was used in salt water, but you never know till you check. That way you'd see if it was from the manifold or cylinder head. I might want to do an oil analysis to see if water is in the oil, if so change it.
 

QBhoy

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Hell you guys are likely right…but wouldn’t it be amazing if it was just the cap and crappy unburnt ethanol (watery) fuel. There’s a hell of a nice chance of it…especially with the symptoms told.
 

1994almeida

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According to the mechanic it must be a small crack in the cylinder head or in a valve.
If it were in the exhaust manifold it would affect more than one cylinder.
Next week the mechanic will disassemble the exhaust manifold and confirm if there is corrosion in the cylinder.
Thanks
 

1994almeida

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According to the mechanic it must be a small crack in the cylinder head or in a valve.
If it were in the exhaust manifold it would affect more than one cylinder.
Next week the mechanic will disassemble the exhaust manifold and confirm if there is corrosion in the cylinder.
Thanks
 

stresspoint

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Hell you guys are likely right…but wouldn’t it be amazing if it was just the cap and crappy unburnt ethanol (watery) fuel. There’s a hell of a nice chance of it…especially with the symptoms told.
i am not up to speed on the ethanol fuel issues as it is not available where i live , probably a subject for another thread , but i would like to know more about this., that being said , if in this instance it was an ethanol water issue it would most likely be across the board ?? .
if you have any link s i would be keen to read up .

i looked at that plug zoomed and it is without doubt rust with a clean burn over it , so that would most likely rule out the cap , but you never know with the many known issues with the crab caps .

another poster suggested the water may have got in through a rusted out exhaust port ,
this is also very possible i have seen this a couple of times at the back of the exhaust valve stem area where the casting is thin on Vortec heads there , it is the same outcome as the leaking intake gasket to the intake runner (miss on start up and rust showing on the plug.
it is very hard to see without a close look, poking with a probe and a bright light
 
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QBhoy

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i am not up to speed on the ethanol fuel issues as it is not available where i live , probably a subject for another thread , but i would like to know more about this., that being said , if in this instance it was an ethanol water issue it would most likely be across the board ?? .
if you have any link s i would be keen to read up .

i looked at that plug zoomed and it is without doubt rust with a clean burn over it , so that would most likely rule out the cap , but you never know with the many known issues with the crab caps .

another poster suggested the water may have got in through a rusted out exhaust port ,
this is also very possible i have seen this a couple of times at the back of the exhaust valve stem area where the casting is thin on Vortec heads there , it is the same outcome as the leaking intake gasket to the intake runner (miss on start up and rust showing on the plug.
it is very hard to see without a close look, poking with a probe and a bright light
If the diz cap is doing what they are famous for…they can cause a miss fire on one (possibly in your case, causing unburnt fuel to gather carbon or moisture from the fuel itself on that one unit) or any other of a number of cylinders too, depending on how they feel at the time. Google or look up on here “crap cap” or mpi distributor cap. You’ll find an array of posts and issues around how bad they are for issues. In my experience they can start causing issues with lumpy running from a cold start….then miss firing occasionally at higher rpms. The number of issues that can cause is almost endless. There is no doubt you could end up with some moisture or unburnt fuel in that cylinder unit, this being the case. Just a thought anyway….
 

QBhoy

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If it’s going to take a while for the mechanic to look further…I’d be tempted to buy a cheap borescope that connects to your phone…then have a look in there to see if there is corrosion on the valves or cylinder liner. Or if any track or trace of a source path of induced water.
 

QBhoy

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No idea why my phone posted a response
Don’t worry about it. Any one of the numerous posts I’ve made…that turn out to be nonsense or silly..is always made by my phone too. Nothing to do with me obviously 😂
 

stresspoint

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If it’s going to take a while for the mechanic to look further…I’d be tempted to buy a cheap borescope that connects to your phone…then have a look in there to see if there is corrosion on the valves or cylinder liner. Or if any track or trace of a source path of induced water.

If the diz cap is doing what they are famous for…they can cause a miss fire on one (possibly in your case, causing unburnt fuel to gather carbon or moisture from the fuel itself on that one unit) or any other of a number of cylinders too, depending on how they feel at the time. Google or look up on here “crap cap” or mpi distributor cap. You’ll find an array of posts and issues around how bad they are for issues. In my experience they can start causing issues with lumpy running from a cold start….then miss firing occasionally at higher rpms. The number of issues that can cause is almost endless. There is no doubt you could end up with some moisture or unburnt fuel in that cylinder unit, this being the case. Just a thought anyway….
i am aware of the many issues those caps can cause , neve have i seen one cause water to enter a cylinder. , as i posted " you never know ".
possibly use a dye penetrant test kit on the cap to find if there a crack ,
although the electrode tracks break internally from people leaning on them when they work on the motors and the damage cant be seen.
as i said , i am not aware of the water in the cheap environmentally friendly fuel .issues.
 
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1994almeida

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Yes, it's the front right cylinder on the starboard side.
After removing the exhaust manifolds, the mechanic found that three cylinders on the starboard side had signs of corrosion.
The engine works.
Now a pressure test is being done on the exhaust manifold to confirm if it has any leaks.
The boat is always used in salt water.
 
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