5.7 Mercruiser Block Drains

Johnson110

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Hi, I can not get the brass drain plugs back into engine block, they are brass and the thread on the block seems shot from salt water how to repair these threads so I can get the brass drains back in it. Thanks for any answers!
 
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achris

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A tap of the same size as the plug... Clean up the block threads and screw the plugs back in.
 

Bt Doctur

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Let me guess you pulled the plugs to drain the block and never put them back in and the threads got a bit crusty.
1/4 inch pipe plug tap used very carefully
 

Johnson110

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Yes I left then out for winter, you say ( 1/4 inch pipe plug tap ) where could I get that tap from I got a 1/2 inch 20 np tap, but it does not work
 

Scott Danforth

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Go yo a hardware store and but the right tap. 1/4" NPT
 

Johnson110

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I got the 1/4 pipe tap the tap will not work what would be the net size up to tap the holes out. Thanks
 

Bondo

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I got the 1/4 pipe tap the tap will not work what would be the net size up to tap the holes out. Thanks

Ayuh,... Why don't it work,... Next size up is 3/8" pipe, which is a huge jump,....
 

Johnson110

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When inserting tap into hole it keeps falling out, it will not screw in even a little bit to bit on threds, can I go to a larger size being 3/8 I can not run engine the way it sits,
 

Dave-R

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Make sure the tap is 1/4" (pipe) not a regular bolt tap. there is a huge difference between the two. Dave-R
 

Bt Doctur

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you must understand there is not a whole lot of depth to those holes. a 3/8ths pipe plug is rather large . You may have to grind off the first few threads to start the tap also.
 

Johnson110

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Thanks at worst case can a heilcoil be inserted for a repair this is very frustrating for me.I really appreciate all the help, on another note why are my reply's not being shown on forum?
 

achris

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1/4 NPT is not the same as 1/4 BSP. And that's why I suggested you take the plug with you when you buy the tap.
 
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Scott Danforth

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there is not enough room between the outer water jacket and the inner cylinder liner for a 3/8" tap. in fact, for most 1/4" pipe taps, you will need to grind the point off of it to get it to start.

you need to get a quality tap.

go slowly, it will clean up the threads. once you get it started, most you should have to do is about 1/2 -3/4 turn of the tap.
 

mr300z87

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Hi I did the exact same thing a few years ago to my 5.7, felt like a total idiot. Fortunately I was able to take a small wire wheel on my dremel tool to clean up the threads enough to screw in the brass plugs although it buggard up the their threads but these plugs were left in until until I got a pipe thread tap I then easily ran the tap in to chase/clean them up. Btw this took a while and there was a lot of bad language being used. Just be patient. I have since replace the brass plug and they are always left in after draining the block and manifold and they always get aviation sealer (Mercury perfect seal) on the threads. Have not had a problem since. Hope this hopes and good luck. Mike
 

Johnson110

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I will try to get a BSP tap as you say, who might have one of these taps on long island?
 

achris

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Any plumbing store.

BSP = British Standard Pipe.
 

Fun Times

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Here's a place in Long island that should be able to help you out. http://www.longislandhardware.com/directions.shtml

As Chris mentioned, take your plug/s? with you into the store and talk to someone in the know.;)

Just to clarify, What year is your engine?

Did you remove the bushing that goes into the block or the smaller brass plug that goes into the bushing reducer? Item numbers 4 and 5 are different sizes.
422-48556--BUSHING , Reducer (.250 To .125)
522-328022--PLUG, Pipe (.125-27)

http://www.mercruiserparts.com/Show...ND+CAMSHAFT(5.7LX+ALPHA/BRAVO)(350+MAG/ALPHA)

37731.png
 

Scott Danforth

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I will try to get a BSP tap as you say, who might have one of these taps on long island?

your motor has NPT (National-Standard Pipe Tap) - Not BSP (British Standard Pipe).
 
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