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Rusted spark plug well/mating surface - is this a concern?

W

wild.coast

New member
While changing the spark plugs on a new to me 2014 Yamaha outboard I noticed that 3 of the 4 wells have a fair bit of corrosion in them, this corrosion isn't just in the 'outer' surface of the well but extends to the machined mating surface against which the spark plug metal washer would seat.

Is this a concern? I'm guessing the uneven corroded surface might mean that the spark plug doesn't seal/seat well causing some leakage and reducing the engine compression?


Any advice on how to clean? I don't want to go to down with a drill-mounted wire brush seeing as brush metal bristles might end up in the combustion chamber. I tried to scrape it a bit with a pick but also worried I might mar up the surface and do further damage
I'm guessing this is a common issue, any thoughts or advice?
 
Turn the flywheel to get a piston at TDC. “Screw” a piece of rag into the sparkplug hole, get it flush, or just a bit below flush. Use your drill, or hand turned brush, then vacumn out the debris.
grab the rag with needle nose pliers, or a dental pick, & twist it out on reverse of the direction you put it in.
Repeat with other cylinders.
 
Edchris177 said:
Turn the flywheel to get a piston at TDC. “Screw” a piece of rag into the sparkplug hole, get it flush, or just a bit below flush. Use your drill, or hand turned brush, then vacumn out the debris.
grab the rag with needle nose pliers, or a dental pick, & twist it out on reverse of the direction you put it in.
Repeat with other cylinders.
Click to expand...

Super helpful, thx! I ended up doing something similar but the trick with putting the piston at top-dead-center is a good idea to prevent the risk of it falling into the combustion chamber. Nice.
 
Robert graham said:
I always put a drop of oil on the threads of the spark plugs before installing them….help stop corrosion!
Click to expand...

Same! I think in this case the corrosion was on the mating surface between the engine block and the spark plug crush/sealing washer. Oil on the threads wouldn't have prevented this sadly - those plugs just needed to be replaced 8 years ago!
 
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