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Help With Brass Drain Plug (Mercruiser 3.0)

S

sterracina

New member
My 1999 SeaRay 180 BowRider has 2 drain plugs (one blue plastic and one brass) that I remove every fall to drain all the water from the engine. Well I lost the brass plug. The engine is a Mercruiser 3.0. I've gone through online parts catalogs and ended up with Quicksilver 22-328022. However I can't get the threads to catch when attempting to screw it in. This screw is on the bottom so you can't really see it when trying to screw it in. The serial number on the engine block is L328943. You can't read any of the serial numbers on the air intake. Is 22-328022 really the correct part? Any idea why I can't get it to catch? It feels like the tip goes in the hole, but it just won't catch when I turn it. The bolts have a red solution on the threads. Is it possible that this is what is preventing the bolt from catching?

When I removed the brass plug in the fall, I decided to replace it because the head of the bolt was worn. I had it in my truck, but the truck was totaled in a rear end accident and I couldn't find the bolt after the accident. I've attached a few pictures.

Thanks,
Sam

Boat2.jpgBoat3.jpgBoat1.jpgBoat4.jpg
 
Ok, where did the plug go?
Block or manifold?

can you take a picture of where it goes?

Typically the brass plug is 1/4 NPT which can be purchased at any hardware store
 
You might have to screw a tap in there to clean up the threads. Take the new plug with you to locate the correct NPT size tap.

Jeff
 
Mine doesn't have the reducer bushing (#14). The bolt screws straight into the engine. I believe the image you sent is for 1990-1994 engines. Looking down at my engine, the brass bolt is a little higher up than the blue wingnut plug. Part number 22-32802 is listed as PLUG PIPE (.125-27). That's what I received but just can't get it to go in. My boat is about an hour away. I can try to get a picture, but not sure how good it will be. I have to use a mirror to even see the hole. The blue wingnut plug is much easier to see and access. It's not upside down.

This is what I have. I think number 2 on this page is my part, just not sure because I can't get the thread to catch.

https://www.mercruiserparts.com/bam/subassembly/30910/2330/80

Boat5.jpg
 
If you removed the plug and left it out the blocks threads have rusted up and you need a 1/4 inch pipe tap to clean the threads. NEVER remove a plug from cast iron and leave the hole open ,always drain and replace it
 
go to your local hardware store, lowes, home depot what ever.

Purchase a few different plugs, they are cheap!

buy two of each. The threads are standard so what is shown in the parts diagrams is true but they all will be the same no matter what source you get them from.

NPT is a standard (national pipe thread) so the 1/8 NPT = .125 x 27.
.125 is diameter and 27 is thread count per inch
most if not all NPT standard has tapered threads.

you want a hex head plug so a wrench will fit. They will also have allen head plugs, but you dont want those

1. Brass, 1/4 NPT hex plug
2. Brass, 1/8 NPT hex plug


NPT typical standard sizes
1/8
1/4
3/8
1/2
5/8
3/4

Look here

https://www.suremarineservice.com/Hardware/NPT-Brass-Pipe-Plugs/
 
In most manifolds and blocks a 1/4 inch is used, on 4 and 6 cylinder models a 1/8 inch plug is used on the underside of the manifold.
 
Thanks for everyone's help. Your responses have been very helpful. BT DOCTOR mentioned that leaving the plug out likely rusted the threads. Using a mirror, the threads have a rusty look. Because of the position of the hole, I don't think I can use a tap to clean the threads (but I've never used a tap before and maybe it's easier than I think). Is there a solution I can spray on the threads to loosen or dissolve the rust. I also may be able to stick a small wire brush into the hole to help scrub the threads.​
 
Get the right plug and screw it in and be done with it.
Maybe add some teflon tape but it should go in just fine.
It takes a while to rust out the threads bad enough that a new plug wont tighten up. Not one winter!!
 
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