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Mercruiser 350 Mag MPI broken plastic drain plug. Next steps.....

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poloperson57

Member
So I was draining my Mag 350 MPI (year 200 model), and as I was re-tightening the one right at the bottom of the engine on the starboard side, it snapped off!

Jeez - I was doing it by feel as I didnt have my light with me, and immediately thought I was in *big* trouble, given the poor access down there. But I grabbed my phone, and took a photo, and actually I think I might get away with this.

The question is - do I try to get the remainder of the drain pug out in situ? If so, how?

Or, do I remove what looks like the nut that the drain plug screws into and tackle it on the bench?

Thanks for any and all advice!
IMG_6903.jpg
 
Or, do I remove what looks like the nut that the drain plug screws into and tackle it on the bench?
Click to expand...
Easiest way is remove the adapter (nut) and then place on a bench to remove plastic plug. Can use a flat tip screw drive or easy out to remove.

Once out replace with same or what's better is use the stainless steel ones from Hardin Marine
PLUGS
 
be careful removing that, it may just come out but you never know. use a 6 pt box end wrench
soak the threads before you try for a few days with a penetrating oil
toss those stupid plastic drain plugs in the trash and just buy the Merc brass hex head ones that come with the adapter that screws into the block
 
As Alldodge posted, remove the adapter, along with the others, then buy the correct size brass plugs. I hate the blue plastic ones with the heat of 1000 suns- they cross-thread easier than anything I have ever touched, they break and if dropped, they're gonna stay where they ended up because I'm not diving after them.
 
Should we start a thread to post service tips & tricks, like using a piece of 1/4" hose with a slit to to slide onto the ceramic insulator, for removing and installing spark plugs when they're hot and/or hard to reach and they didn't come out with the socket? When space is tight, this is much easier that trying to do it with a socket on an extension or on a wrench.
 
poloperson57 said:
Great advice everyone. It's mighty cold, dark and miserable here at the moment so I'll tackle this when it's warmed up a bit.
Click to expand...
IMO, seeing things in a bilge is overrated. I feel around and if it doesn't want to go after about 1/2 turn, I remove it and get it right.

That's how I learned to hate the blue plugs.......:)
 
Ayuh,..... The blue plastic plugs are 1/2" - 13,.....
I bought some 1/2" -13 by 1/2" long ssteel cap screws, tacked 1/2" ssteel washers to a groove I ground into/ onto the boltheads, then a ssteel washer held onto the threads with a rubber o-ring,....
Now I have drain plugs, much like the ones that can be bought at better marine supply shops,....
 
I don’t know what Mercruiser was trying to accomplish by using the plastic plugs other than cost reduction because the metal ones (brass) don’t corrode or seize even in salt water use!
 
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