Hull Drain Plug

Kevin, can you better explain what is damaged and driving you to replace parts? If the plug is the only thing damaged, just replace that. If its the port, then thats a bit trickier. Can the threads be cleaned up rather than replace it?

The port is in fact installed from the bottom- there are 3 small bolts that go through the hull, as well as sealant on both the port and bolts. With the engine in place, it might be a real pain to remove- could take some force.

I'd put 5200 on the new one when installing (NEVER use silicon below the waterline!!!). 5200 is pretty messy- wear disposable gloves and keep plenty of rags and acetone on hand to clean up the excess.

There are tapered taps for those tapered pipe threads, dont go deeper than needed and dont start from the wrong side!!!

I agree with Eddie regarding using a NPT tap to clean up the threads rather than replacing the thru hull. The last NPT tap I needed was a 1&1/4" for the Flexifour exhaust. Got it off Ebay real cheap! I have a pretty complete set up to 2" now. They always are handy.

Well been there! My plug had a square head and no handle and was frozen...
Think was one of the first things i solved with the help of the site.
So i had to remove the port with the plug and then work it loose in a bench press. Then welded a t handle on the plug and installed everything back using 5200...never a problem since then

Does it leak??? My pet peeve is over tightened fasteners of any kind. When mine gets tight I don't even go more than maybe like 1/8 turn past that. If I cant get it out by hand on the lift then its way too tight. No tape or sealant its a brass NPT fitting.

The only time my plug is in is when the boat is in the water. Otherwise I want any water that finds its way in to Leave as soon as possible. I never thought about it but this also keeps the plug from seizing.

Do like Joe said run a tapered tap through the port. I did that to my '85 during rebuild worked like a champ.
I remove my plug after trip hand tight is all it should be no tape or anything else on the threads.

If the threads have been crossed the tap may have to "cut" out some material, making it a bit of a rough fit, but if the tap spins in and out by hand when you're done, the new plug will too.

I'm with Zach, I hate having to bend my arm in there and struggle to get it out so I barely tighten after it's snug.

8122pbrainard wrote: gun-driver wrote: Do like Joe said run a tapered tap through the port. Certainly a good idea as I confirmed BUT, he didn't nor have I mentioned the need for chasing the threads on the male plug!!! Chase the plug too especially if as I mentioned it's been cross threaded! Find a plumber friend with a 3/4" NPT die!    Even with brand new pipe, I've seen male threads not in the greatest shape.

I did chase the plug when I did mine because I have a pipe threading set but I didn't mention it because I thought he was buying a new plug.

8122pbrainard wrote: 63 Skier wrote: If the threads have been crossed the tap may have to "cut" out some material, making it a bit of a rough fit David, Check the thread engagement length of a normal 3/4" NPT thread. Do you really feel it's a concern? I don't! How many brass pipe threads have you cut? I've cut plenty through the years. I lost count a long time ago!

You're right Pete, limited experience with brass, have cut and chased lots of steel thread. I'm not sure what you mean though, what does the engagement length have to do with the quality of the threads in that engagement? What I'm saying is if the threads are scored from the cross threading, a tap can't clean that up completely and it may make for a rougher fit than new thread.

Pete's right takes less than 1/2 turn to clean up NPT theads.Assembling engine now and always chase every thread before assembling.Only place I use,any sealer is dissimilar metals never brass to brass

63 Skier wrote: Well thanks for the info, always willing to learn. I'm still slightly skeptical, will be interested to read how it works out for Kevin. I still picture a drain plug that seals perfectly, but is a bit raspy going in and out.

David,
Chasing the threads should give you a nice smooth fit however since you are concerned, use an old toolmakers trick to get them real smooth. Put some lapping compound on the threads and run it in and out a few times.

Follow up. I know I hate reading these threads only to never know the outcome. Well, the tap arrived today and sure enough it ran through by hand effortlessly. The new drain plug goes 3 3/4 complete turns so I think we should be all set. Thank you all for the speedy responses, ideas, and warnings. You probably save me a ton of unnecessary work. I still don't know what caused the seizure but everything is fine now.

Bri892001 wrote: I've noticed the phenomenon of the plug getting tighter somehow over time. It probably has to do with heating cooling cycles under the doghouse, with the cooler lakewater on the other side.

Sorry Brian but I'm not going along with this theory! As mentioned, I still feel someone cross threaded the plug.

My plug is in transem from the outside.Which way should I turn to avoid seizing ?