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Stripped Manifold Drain Plug Thread
Well I must have set a record for the longest "1 hour" winterising ever!
(following the steps in Don's manual would indeed take an hour or less..if only the venerable old engine would co-operate!)
After removing the three drain plugs, and putting two back easily, the third, the aft drain plug (just behind the starter motor) would not go in at all. It turns out the thread in the casting was either slightly damaged or just full of dirt. Eventually after finding a local place that sells them, it took three minutes with a 1/8 tap and a new plug and I was finally ready to put the antifreeze into the cooling jacket.
Once that was done, I noticed that there was a slight leak around the manifold drain plug (rear of the engine, port side - 7/16 hex head 1/8 inch npt). I tried tightening it and ... the entire plug came cleanly out with no purchase at all left in the casting. I suspect the leak had allowed enough oxygen in over time to corrode the threads..whatever the reason, there are is now nothing left inside the casting for the plug to obtain purchase and my new 1/8 inch tap won't save me this time since it goes in and out of the hole quite cleanly!)
I wrapped a lot of teflon over the plug and it seems like this will hold over the winter. But clearly I need a better solution before spring.
A couple of questions:
Any suggestions for repair?
Do I need to drill into the casting and tap a new (and larger) hole? I am not sure I have enough room to do this or whether the casting is such that a larger hole will interfere with other workings of the manifold or jacket. Nor am I comfortable I have the skill to avoid causing even more harm.
Do I need this drain plug at all or can it simply be more or less permanently sealed? If so, is there some kind of epoxy/welding material (like the kind plumbers use for waste lines that would bond well and handle the heat and pressure?
My preference would be for a solution that preserves the functionality of a removable drain plug but is relatively easy to implement without the need for a welding torch or removal of the engine from the boat. BUt that may be too much to ask for ...
(following the steps in Don's manual would indeed take an hour or less..if only the venerable old engine would co-operate!)
After removing the three drain plugs, and putting two back easily, the third, the aft drain plug (just behind the starter motor) would not go in at all. It turns out the thread in the casting was either slightly damaged or just full of dirt. Eventually after finding a local place that sells them, it took three minutes with a 1/8 tap and a new plug and I was finally ready to put the antifreeze into the cooling jacket.
Once that was done, I noticed that there was a slight leak around the manifold drain plug (rear of the engine, port side - 7/16 hex head 1/8 inch npt). I tried tightening it and ... the entire plug came cleanly out with no purchase at all left in the casting. I suspect the leak had allowed enough oxygen in over time to corrode the threads..whatever the reason, there are is now nothing left inside the casting for the plug to obtain purchase and my new 1/8 inch tap won't save me this time since it goes in and out of the hole quite cleanly!)
I wrapped a lot of teflon over the plug and it seems like this will hold over the winter. But clearly I need a better solution before spring.
A couple of questions:
Any suggestions for repair?
Do I need to drill into the casting and tap a new (and larger) hole? I am not sure I have enough room to do this or whether the casting is such that a larger hole will interfere with other workings of the manifold or jacket. Nor am I comfortable I have the skill to avoid causing even more harm.
Do I need this drain plug at all or can it simply be more or less permanently sealed? If so, is there some kind of epoxy/welding material (like the kind plumbers use for waste lines that would bond well and handle the heat and pressure?
My preference would be for a solution that preserves the functionality of a removable drain plug but is relatively easy to implement without the need for a welding torch or removal of the engine from the boat. BUt that may be too much to ask for ...
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