Drain plug: For Welded Aluminum Boat...Threaded? Compression?

[TMan]

Hey there.
I need to install a drain in my welded aluminum boat.
What do people here use? Compression type? Or threaded?
Compression plugs seem simple enough to find.

But..

...If threaded....where do you get the fittings from?
The plugs seem easy to find in Aluminum, stainless or brass, but the part that is threaded I can't seem to locate.

Do I have to make my own from some aluminum pipe and get it welded into place?

Any advice is great.

Thanks,

Trevor

 

[markfarley]

Mine is a threaded stainless plug in a welded aluminum flange. the flanges can be found at most industrial supply places or welding supply shops.
They are referred to as "sculley flanges" and the pipe style is called a "weld-olet". I use lots of prop shaft grease on mine, not to tight, never a problem.

 

[TMan]

Mine is a threaded stainless plug in a welded aluminum flange. the flanges can be found at most industrial supply places or welding supply shops.
They are referred to as "sculley flanges" and the pipe style is called a "weld-olet". I use lots of prop shaft grease on mine, not to tight, never a problem.

Hey that's great to know.
Do you end up using anything to stop corrosion? Grease?

 

[TMan]

Hey that's great to know.
Do you end up using anything to stop corrosion? Grease?

Wait.....did not read until the end....squirell......
sorry. Lots of grease.

 

[gungadin]

Years ago when I had a welded aluminium boat, I used a piece of aluminium plate (scrounged), can't remember how thick it was, about 1-1/2 inches I think. I welded it to the transom on the outside and then drilled and tapped it for 1 inch pipe and used a plastic pipe plug and teflon sealer on the outside. On the inside I zip tied a compression plug to the wiring. (as a back up). Now my boat had a lip on the bottom of the boat that extended about 1/2 inch past the transom, so I needed to fit it carefully. The only problem was I had to sponge out any water that would not pump or drain out as the bottom of the drain was not flush with the bottom of the boat.

 

[ReelSlim]

I have both styles of plugs in two different boats. I have a compression foam style one in a 15' SilverStreak that is a neat concept but I have to admit it's a bit of a pain. I have looked around and haven't seen one for a replacement when the time comes. It's 1.5" at least and might have to ask them where they get them...lol The big issue that it's sort of a two handed install and that means I have to get up in the boat to do it cause I can barely reach it from the ground and it always spins while I tighten it. On my other boat he welded in a proper fitting that has a 1/2" threaded connection that a well taped SS plug goes into. A much easier system in my opinion and is why it's used on most boats I'm sure. The one for my SilverStreak looks a lot more slick and I'm sure some work went into installing it but not a fan overall.....lol

 

[Whole in the Water]

I use a compression plug and I trailer my aluminum boat. Simple, easy, cheap, no corrosion or voltage issues because of dissimilar metals. If you keep your boat in the water for long periods that may be a reason to go threaded. If not, why bother?

 

[TMan]

Thanks guys.

When I get it worked out and installed I'll post a pic.

I'm leaning towards the threaded plug, but even so, with compression types or SS plugs I worry about the dissimilar metals and corrosion.
Do people ever use plastic plugs? UHMW or the like?

T.

 

[Chuck]

Mine has aluminum threaded flange welded in place with a stainless plug. I carry a couple compression type plugs for back up in case threads end up getting damaged. Compression style can be installed on the inside or outside of the transom.

 

[ReelSlim]

Here is the large compression style plug in my SilverStreak. Like I said it’s a bit of a pain to put in but I should probably put some light grease or Oring lubricant on it to possible make it a bit smoother to install. With the SS plug it is isolated from directly touching the aluminum with several layers of Teflon tape. The rest of the boat has anodes on it so I’ll just keep an eye on it but not too worried to be honest. The boat was in the water for a few months this summer. I was happy to see when I pulled the boat that the zincs had good wear on them all around so they are doing their job. Depending on your set up either will be fine.

 

[Sentinel]

For the threaded in ss plugs here is the best thing I have found for the threads. It is the best stuff to use on any ss fastener going
Into aluminum threads for that matter.

https://www.crowleymarine.com/parts/15896.cfm

 

[Chasin' Dreams]

I use plastic male plugs in my female threaded aluminum drain hole. Never had a problem with them but they are pretty tight. I carry extras cause if you do remove and re install them several times the heads of the plastic plug can get warn where sockets could spin over the edges.

 

[Filletandrelease]

The tin boat moored beside me sunk earlier this year. The compression plug had rotted away.

 

[staying alive]

I have a 23’ crest liner aluminum boat it has a threaded male plastic plug into a threaded aluminum plate , never had any issues , I trailer it if that makes a difference don’t know

 

[CIVANO]

Get a plug socket do you don't round off the shoulders of the plug

 

[Chasin' Dreams]

Get a plug socket do you don't round off the shoulders of the plug

Like a spark plug socket?

 

[CIVANO]

It is 4 corners - square opening. It fits the square end of a male plug. I learned the hard way with an alum plug and regular socket. My plug square male end is 9/16 and the socket is square 9/16 going on a 1/2" drive socket set.

 

[Chasin' Dreams]

It is 4 corners - square opening. It fits the square end of a male plug. I learned the hard way with an alum plug and regular socket. My plug square male end is 9/16 and the socket is square 9/16 going on a 1/2" drive socket set.

Ah got it ok cool ya I think I have a set of them somewhere. Thanks for the heads up on that.

 

[TMan]

This has been great!
Thanks everyone.

Trevor

 

[trophywife]

bronze with lube.