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block plug


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de-winterized today and confirmed that the port side block plug is stripped. when I pulled the old one in the fall I found it to be bad so I ordered a new one and now found the block theds are also messed up. I got the new one in and it's not leaking so I hope i'm good for the seson. my question is can you re-thred the block so a petcock can be installed. the starbord side has one already.

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de-winterized today and confirmed that the port side block plug is stripped. when I pulled the old one in the fall I found it to be bad so I ordered a new one and now found the block theds are also messed up. I got the new one in and it's not leaking so I hope i'm good for the seson. my question is can you re-thred the block so a petcock can be installed. the starbord side has one already.

I would shy away from petcocks. They have a tendency to plug up with debris and may not let all of the water drain from the block. The block plugs should be brass so they shouldn't strip the threads out of the cast iron block. The holes in the block are tapped for 1/4" national pipe thread. I would consider drilling and tapping to the next largest size and buying larger brass plugs. Is youe engine an EFI engine? If it is you have to retain a 1/4 NPT hole for the knock sensor. If that is the case, you can drill and tap to a larger size and use a reducer bushing to get back to 1/4" NPT.

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Usually its from someone being lazy putting the plug back in and cross threading it.

I've found a 1/4 NPT tap run in there carefully will fix the problem usually. It would be an awkward spot to get a drill in so that would be my last resort.

-Chris

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Usually its from someone being lazy putting the plug back in and cross threading it.

I've found a 1/4 NPT tap run in there carefully will fix the problem usually. It would be an awkward spot to get a drill in so that would be my last resort.

-Chris

:plus1: What he said. Your block probobly isnt stripped but the threads are full of the engine plug brass from being cross threaded. With either plug you can chase the threads with a tap to clean them out. will be good to go after that.

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  • 4 years later...

Bringing an old one back......what say the crew, petcock or no? Was thinking about going this route this winter when I winterize but then I found this post.

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Bringing an old one back......what say the crew, petcock or no? Was thinking about going this route this winter when I winterize but then I found this post.

I looked for an answer on this on Monday... opinions range from "It only takes 15 minutes to winterize as-is, so don't bother" to people talking about this kit (although I'm unclear as to how it would really work)

http://www.skidim.com/EASY-DRAIN-INDMAR-FORD-GM-PCM-GM/productinfo/MCM000/

(If anyone knows where you would install these 4 fittings, I would be interested in knowing!)

You'll get plenty of opinions here though!

I decided today that I would give this (1/4" NTP male ball valve) a try for the starboard engine block plug, as mine is in terrible shape and I want to get debris out of the engine cooling system a few times a season. It does add a risk of getting plugged from debris, so you still need to put a stick or something inside to keep it draining. Its a cheap brass valve and is a full valve, so I hope it limits the clogging.

http://www.amazon.com/dp/B00835OJBA/ref=biss_dp_t_asn

Every Car / Boat guy I know personally (and many on the forum) have said not to mess with the port side engine block knock sensor plug (some people mention adding a T-fitting with a drain valve and don't have problems - most recommend against it) because of the many issues it can cause - so I'm leaving this one alone.

As for the rest of winterizing, I use the heater/shower mod mentioned on the forum (hose fittings that are easy to disconnect) and the manifold hose fittings that came on the boat and then just disconnect the rest of the hose clamps manually and it does not take long at all. Hope this helps.

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Got to totally agree with no petcock. IME they just crud up and turn into a solid plug any way. Plus depending on what it is made up you may end up with galvanic corrosion turning it into a plug or worse yet eventually starting to leak. JM2C

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I looked for an answer on this on Monday... opinions range from "It only takes 15 minutes to winterize as-is, so don't bother" to people talking about this kit (although I'm unclear as to how it would really work)

http://www.skidim.com/EASY-DRAIN-INDMAR-FORD-GM-PCM-GM/productinfo/MCM000/

(If anyone knows where you would install these 4 fittings, I would be interested in knowing!)

You'll get plenty of opinions here though!

I decided today that I would give this (1/4" NTP male ball valve) a try for the starboard engine block plug, as mine is in terrible shape and I want to get debris out of the engine cooling system a few times a season. It does add a risk of getting plugged from debris, so you still need to put a stick or something inside to keep it draining. Its a cheap brass valve and is a full valve, so I hope it limits the clogging.

http://www.amazon.com/dp/B00835OJBA/ref=biss_dp_t_asn

Every Car / Boat guy I know personally (and many on the forum) have said not to mess with the port side engine block knock sensor plug (some people mention adding a T-fitting with a drain valve and don't have problems - most recommend against it) because of the many issues it can cause - so I'm leaving this one alone.

As for the rest of winterizing, I use the heater/shower mod mentioned on the forum (hose fittings that are easy to disconnect) and the manifold hose fittings that came on the boat and then just disconnect the rest of the hose clamps manually and it does not take long at all. Hope this helps.

I think the link you posted for skidim is for the older TBI boats. IIRC, my old SSLX had (4) block drains and only one was a knock sensor. It was quite different than my multi-port EFI in the RLXI. Don't know....I may be incorrect.

Edited by inlandlaker
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I looked for an answer on this on Monday... opinions range from "It only takes 15 minutes to winterize as-is, so don't bother" to people talking about this kit (although I'm unclear as to how it would really work)

http://www.skidim.com/EASY-DRAIN-INDMAR-FORD-GM-PCM-GM/productinfo/MCM000/

(If anyone knows where you would install these 4 fittings, I would be interested in knowing!)

Reminds me of mercruisers old single point block cracking system ;) Fittings that are designed to be run together with a hose to a single drain point and are near impossible to check for blockage. I would never put anything in the drain path that reduced the diameter or introduced 90 degree direction changes. Both could trap debris and clog.

If you really wanted to make it a little quicker to drain then you could replace any plugs with the old mercury blue plastic plug system. The black scorpion in my father inlaws response has 7-8 of them that you just remove with your fingers.

  • Like 2
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That's exactly what I'm doing, I actually purchased one of the Mercruiser blue plastic t-handle plugs. They have about 6-8 of them on the V8 to drain the engine at various points including the block. It should fit, but haven't tried yet.

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That's exactly what I'm doing, I actually purchased one of the Mercruiser blue plastic t-handle plugs. They have about 6-8 of them on the V8 to drain the engine at various points including the block. It should fit, but haven't tried yet.

Should fit on the older engines like yours, newer engines just don't have all those drain points and rely on removing hoses. The block plugs on the Black Scorpion actually screw into a brass adapter fitting, not straight into the block. For reference the plugs (as I recall) on the black scorpion (2004 LXI) are:

2 exhaust manifold plugs

2 block plugs

2 plugs on the raw water pump (Engine mounted, not crank mounted)

1 plug on the angled fitting leading to the heater

1 plug on the fuel cooler

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I've used a brass petcock for years with zero issues. It's far easier than messing with a plug every year. How would they only let some of the water out? It either drains or it doesn't.

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I've used a brass petcock for years with zero issues. It's far easier than messing with a plug every year. How would they only let some of the water out? It either drains or it doesn't.

More than once (in the past 40 years) I've stuck a screwdriver in a block drain hole after it's stopped draining, dislodged some debris, and drained another quart.

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More than once (in the past 40 years) I've stuck a screwdriver in a block drain hole after it's stopped draining, dislodged some debris, and drained another quart.

Every time for me

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Every time for me

More than once (in the past 40 years) I've stuck a screwdriver in a block drain hole after it's stopped draining, dislodged some debris, and drained another quart.

Not one time have I had an issue. You guys must go in dirty water?

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Not one time have I had an issue. You guys must go in dirty water?

The problem is that water does drain out, then stops and you think it's all drained. You can't really verify with a petcock in the way. I've only dislodged a clog a handful of times in many, many attempts. The risk (cracked block) for the small amount of convenience isn't worth it to me.

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I used petcocks on my old MC for almost 10 yrs with no problems at all. I blew compressed air into the petcocks once in a while. Occasionally I'd get a bit more water out of it but certainly not every time.

On the Malibu, the 2 openings in the engine are used by the shower & knock sensor so I've never bothered to change things.

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Just got finished winterizing my boat and this was one of those times that the water stopped draining on one side, then drained quite a bit more after dislodging a clog with a small screwdriver.

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