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Spark plug corrosion?

4104 Views 15 Replies 5 Participants Last post by  Smackdaddy53
Purchased a boat and motor back in July. 2000 Yamaha 60HP 2 stroke. Of course I did a few things (water pump, spark plugs, etc) and now 5 months later I was just checking under the cowling and I see corrosion around the spark plugs on the block. I had noticed that there was some type of gasket/ putty that was around them the first time I changed them but scraped it off. Anyone have any suggestions on how to stop this or why it’s happening? Maybe water in the cylinders??

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· Zephyr Cove is on FIRE!
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Check compression, should be around 125-130 in each hole. Keep the plugs sprayed with CorrosionX along with everything else under the cowling. The bottom plug always gets rusty first if you don’t. Not sure why you have that buildup but compression test and new plugs. Don’t cheap out, buy the NGK that are specified for your motor, they aren’t expensive.
 

· Zephyr Cove is on FIRE!
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That head has been removed and not reinstalled properly. Those bolts to hold it in are a mix of SAE SS, factory metric hardware, and it appears to be SAE zinc plated grade 3, 5, and 8...basically a hodge-podge of bullshit.

The heavy corrosion you are seeing at the base of the plugs is from the water jacket cover leaking around the plug locations. Likely, that gasket wasn't replaced along with the head gasket. order both, clean the surfaces, and reinstall. You are relegated to using the hardware sizes now in use (thought they can all be SS) as the SAE ones will have been drilled an tapped.
Good eye!
 
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