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5inthesun

Color me stupid

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5inthesun

So, me and my son were getting the boat ready. Putting all the hoses, plug's, etc... back in. I got the knock sensor in on one side and I am yelling at my son not to cross thread the plug on the other side. He couldn't get it started I went over to show him how it should be properly done. Of course I cross threaded it and popped the entire plug out. Tried to go to home depot and get a 1/4 inch plug from the pluming area. Does anybody know if that is a different thread pattern? I couldn't seem to get it to start almost like it was a hair to big. I may end up cleaning it with a wire brush or carefully re-tapping it. I still don't think it would fit though.

Thoughts?

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Cap305

Should be NPT thread. Standard brass fitting should do it. I replaced mine last year. Tapping it to clean out any gunk in the threads may help too. I left the plugs out of my block two winters ago and had to clean out the corrosion with a tap before I reinstalled the plugs.

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5inthesun

Is everyone 100% sure it's 1/4 NPT? Just want to make sure I get the right tap.

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Cap305

Not sure if you have one close to you but Harbor Freight sells a tap/die kit for under $20. You can take the old plug and put it in the 1/4" die to make sure. I've used mine several times. Good money spent. With the tap make sure you do it very very gently. You don't want to cut new threads, just free up the existing. One thing you may want to try before you go out and buy a tap is to WD-40 the block threads first. May clean out the existing rust a bit.

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dfarhood

I could be wrong, but I always thought plumbing threads were tapered to help create a seal. Using a normal tap and die set would not leave the threads tapered in the same way so doing this could create a slow leak.

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5inthesun

Anyone? I bought the tap proposed and plan on doing this in the next few days. Don't want to make a mistake here.

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justgary

Well, if you tap it 1/4 NPT, it *will* be 1/4 NPT. Personally, I'm 100% sure it is already. The tap should just chase the threads, and not really remove any new metal.

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electricjohn

Stick something in the hole to see how much depth you have for retapping. You may need to use a bottom tap.

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5inthesun

Used NPT tap and it worked no problem.

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