Blue Plastic Drain Plugs

Summerwind

Summerwind

New Member
Aug 21, 2008
275
Phila
Boat Info
2008 Formula 310 Sun Sport
Engines
377 x 2 w/BIII
:smt100 I over tightened the thermostat drain plug and the wings snapped off. :smt013 It’s threaded and not Leakey.

These plugs are a real PITA.

Now, how do I remove the stud to install a new blue plug?

TIA
 
I do not know what you mean by the stud but is it possible to take a screwdriver or punch and try to back it out? I have them on my boat and I agree with you.

Glenn
 
Ha, same thing happened to me. They get brittle and the wings will snap off in your hand and all you are left staring at is a blue cone.

take a pair of vise grips and clamp into it. Or you can file flat spots on each side and take a pair of plyers to it.

depending on how brittle and how tight that sucker is, you may snap off the head leaving the threaded portion in. Fortunately, the whole piece is brittle and with a little time, you'll be able to dig that sucker out and pick out the pieces.

I should also note that the threaded portion is hollow. it has a hole right in the middle. So you can take a phillips head and dig in there and remove some of the plastic. Then when you've got the hole big enough, you can take a flat heat to the edge and break a piece of the plastic off and the rest will come out easy.
 
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Yeah, there's no real trick to getting it out. But, it shouldn't be that hard - do whatever is most convenient.

When putting these plugs in, snug is all that is needed. They seal with an o-ring.

I always keep a couple extra of these on the boat.
 
Thanks guys, but it’s a clean flush break, the thread are flush even with the surface of the thermostat, so there isn’t anything to grab with the vice grips.
Some really old one armed skipper (no, really) at my marina said that "they" have a screw that’s counter thread? That can remove the plugs threads?
 
try a really small tap??? There are kits to remove bolts/screws that are stripped.
 
A tap would be my next choice, too. If you don't have one, try a screwdriver held at an angle to the flat, blue area - towards the outside of flat area (not the middle). Tap/hit the screwdriver with a hammer. I'm not sure I'm explaining this correctly, but hopefully you get the idea. You're trying to unscrew the plug by using the hits on the screwdriver to twist it.

If you make a small indentation (like with a drill bit), I think a small, "star" headed screwdriver might work better - less likely to split the plastic. Even something like a 1/8" piece of metal rod.
 
Lazy Daze said:
A tap would be my next choice, too. If you don't have one, try a screwdriver held at an angle to the flat, blue area - towards the outside of flat area (not the middle). Tap/hit the screwdriver with a hammer. I'm not sure I'm explaining this correctly, but hopefully you get the idea. You're trying to unscrew the plug by using the hits on the screwdriver to twist it.

If you make a small indentation (like with a drill bit), I think a small, "star" headed screwdriver might work better - less likely to split the plastic. Even something like a 1/8" piece of metal rod.
Click to expand...

Yes, I understand and I think a star head might just do the trick.
 
You could grind or cut a slot in the head of the plastic plug using a thin blade grinder or hack saw and try using a slot screw driver. That would work well... Then if it did not, go with the tap... they are hollow inside and it won't take much to pop through the head.

the ole guy you mentioned uses a counter drill screw. Real easy to find in a hardware store and would/should also work well.
 
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I think the only way you are going to get it out is to pick piece by piece out. the plastic is just too brittle for anything to grab it. If you snapped of the whole head with your fingers, every tap or bit is just going to grind more plastic out. At least that was my experience.
 
Does this suggest (or is it in some part of the manual I've not seen) that we should be replacing these blue plugs every couple years or so, so they don't get brittle like this? (I would imagine heat/age would be the attributing factors here?)

-VtSeaRay
 
Well I can tell you 5 years is too long. I'll be replacing them every couple of years I think. If they are still "good" i'll put them in my spares bag.
 
Same thing just happened to me, good thing I was running it in the yard, because when I tried tightening it it snapped off in my hand and water started flowing in. I just bought some cheap screw extracters and it turned out by hand. The old ones were missing the o rings which is why they were leaking. I think they were the originals so I replaced them all.
 
At the bottom of my manifolds I had plastic elbows with the Blue drain plugs in the bottom, I'm FWC. On my Stb engine, one broke off all by it self and emptied the antifreeze into the bilge, I overheated and shut down. In another incident I tried to stop a drip and broke another blue plug on the Port engine, another mess. This year I bought brass replacement elbows from Mercury Marine. I paid $40 each. It may be a lot but its the best $160 for piece of mind let alone the mess, and having to come in on one engine. If they made the Blue plug solid and without the hole in the center, it would not make a mess. Mercury told me they don't know how those type of elbows were on the boat, they are used for Raw water cooling drains.
 
Love these type of threads..I learn something, then realize I don't want the same problem and it always ends up costing me money... So.. if anyone else out there is looking to replace the blue caps on a 5.0 MPI, this is the part number to search for: 806608A. Good news is that these are only a couple of bucks each..
 
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