Block Drain Plug

[_X_]

92 Nautique. When we put it away last fall there were no issues when removing the plugs to drain the block.

Went to put them back in this weekend and the back plug, drivers side would not thread in at all. Being smart fellas we took out the front door me and tried it. No go. Same result with the opposite side plug.

The treads don't appear cross threaded and what we can see of the hole looks good. Even tried a brand new plug with no luck.

Are we gonna have to end up retapping? And if so what size?

Here are a couple shots of the plug and hole.












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[Skidave]

I have used the quick drains for years. That way you are not screwing and un-screwing every season.

http://www.skidim.com/mobile/EASY-DR...ctinfo/MCM002/

You may need to clean your threads in your block with a tap. I know it is NPT threads, and as I recall 3/8.

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[_X_]

Do I need a special tap for the NPT?


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[DaveNH]

NPT is national pipe thread. It's completely different from machine thread. Some people would call it a 3/8" pipe tap. Easy to borrow, easy to find at hardware or auto parts store.

I second the use of drains. Your plug thread is mashed, that's why it won't thread in, and likely damaged the block thread. A tap will fix it easily.

[Fgroce]

I agree buy the NPT tap and chase the threads, but do not go all the way in, just enough to clean up the threads, Also buy new plugs from the hardware store.

[_X_]

Thanks guys. Wife stopped at Napa to ask about the size. She will stop tomorrow and get the tap. We got a new plug from m the local marine store this weekend. Though when she stopped there to ask the service department what they thought the guy told her it was the wrong plug, even though the parts guy said it was. Old one required a wrench the new one is an Allen wrench.


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[Skidave]

Becareful with the Allen style. There are issues with the length (depth) of the Allen. You don't want it to go too far into the block and not be able to remove because you lost the thread contact. Yes, I know the casting is not that deep, but I know a guy who dropped a fogging straw into a cylinder one time (uh, yeah that was me). No matter how careful you are, a few simple things can ruin your day.

Order the quick drains and get some vinyl tubing from your hardware store to run out your bilge hole. Draining your engine will never be easier and cleaner.

[DLafont]

The drain valves you guys are recommending look awesome, makes you wonder why the boats aren't equipped with those from the get-go...

[_X_]

Thanks guys. Wife got the tap so one of these nights I will get it cleaned up. Probably use the Allen style plug so we can just get the boat in but those quick drains look pretty nice for future use.


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[Fgroce]

Put some teflon tape on the threads and it will seal up nice. Just do not get too carried away with how deep you go with the tap, just enough to clear the threads.

[_X_]

Thanks Fgroce, I was planning to go very shallow at first, try the plug and then tap further if needed.

[Fgroce]

Just be careful about using the quick drain plugs, if one of them accidentally plugs up when you go drain your block to winterize it you will have a real bad spring. Just my opinion.

[DaveNH]

I always fish the drains with a wire just to be sure. There are different styles of drains/petcocks, and you want a full flow style to avoid plugging up like Fgroce mentioned.

On a '92 Nautique those drain plugs come out and go back in 25 times by now if winterized every year. While with care it can be done, that's a lot of in and out for npt thread. The taper is designed to seal and puts a lot of stress on threads. Nobody would argue that pulling a plug is the best draining method as you have full flow out of the hole with no loss of flow area, but in practical application it's just too many uses of the same threads IMO.

[_X_]

I've wasted probably 6 hours on this one plug.

Tried two different taps, had a machinist clean up and sharpen the threads on the plug. I can get the plug to sorta thread. But as soon as socket touches it it falls out.

Local marina shows me no love and is high on labor rates so tomorrow it goes to my auto mechanic. I figure a Ford block is a Ford block and an auto mechanic tapping is the same as a marine mechanic tapping.

Honestly a 10 minute spring project should not have led to this amount of angry beer drinking!


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[DaveNH]

You aren't trying to re-use that plug, are you? The old plug needs to be thrown out, and a new one installed, or better a drain as discussed above.