Plug for aluminum boat

[JASinIL2006]

Hi all, I recently purchased a 14' aluminum v-hull rowboat (a 1968 Sea Nymph, I believe!). It has a threaded 3/4" hole in the bottom of the boat about 4" in front of the transom. Of course, there was no plug when I bought the boat, so now I'm trying to figure out what to use. I have one of those rubber plugs that expand when you crank it down, but it doesn't look like it will make a great seal. I'm wondering if I might be able to find some threaded plug to put in, but I can't find any in aluminum and I'm concerned about galvanic corrosion if I use some other metal.

Any ideas about how to plug this? This boat gets us (and our gear) across a lake to our cabin, so we really need it to be safe. The boat will have a small outboard - 9.9 HP - on it as well. We use the boat about 4 weeks out of the year. The rest of the time it sits, uncovered, upside down on the shore of the lake.

What would be best? I even picked up some PVC plugs, but I'm not sure how well they'd work. The last thing we want is to be halfway across the lake and have the plug fail.

Thanks for any ideas!

 

[Texasmark]

Re: Plug for aluminum boat

Well, if it's a standard pipe thread and you found a PVC one, then use it and have a galvanized steel or brass one as a backup. Then you will not have to worry about corrosion. Per a Military manual for corrosion prevention, Zinc and Alum are in the same metallurgical category (Cat II, per MIL-STD-454) which means that they can be used together. So, since steel pipe plugs can be purchased as either zinc or galvanize plated, which is also Zinc, get one of those. The rubber plugs are intended for a slick cylinder to seat against, not threadded so you are correct there. I doubt that wrapping the plug in teflon tape would do that much for corrosion prevention, but it might.

HTH,

Mark

 

[roscoe]

Re: Plug for aluminum boat

Yep, get a metal pipe plug and screw it in.

If you want, use a marine sealant, or JB Weld to secure it forever.

We had a habit of accidentally knocking the rubber plug out with our feet while fishing.
My dad JB Welded a plug in, back in the mid sixties, and the plug is still secure to this day.

Can make emptying the boat of rain water a bit of a hassle.

 

[smokeonthewater]

Re: Plug for aluminum boat

get a brass or bronze pipe plug.... no need for aluminum

they can be bought at a hardware store or or you can get them from a boat supply with a T handle

If you look under the hole on the bottom of the boat there is likely a clamshell around it so that you can pull the plug while running at speed and drain any water in the boat.

 

[Scott Danforth]

Re: Plug for aluminum boat

I would go brass. there were even brass plugs with cast on wings just for the drain hole. http://www.iboats.com/Garboard-Drai...3650635--**********.609486806--view_id.470216

if you are worried about corrosion, then you could also go glass-filled nylon.

 

[robert graham]

Re: Plug for aluminum boat

Lots of ways to skin this cat, but my aluminum jon boat has a 2" diameter drain in the transom, and I use the black rubber pipe plug with the metal washers either side and a big thumb screw to tighten it down....works fine so far. You can install the plug from inside or outside of the transom. The JB Weld/permanent plug wouldn't work for my purposes because I have to be able to remove it to drain any water(from rain or spray) out of the back of the boat. You may also need to drain the boat to wash out fish guts, old bait shrimp, etc. Of course the brass threaded plug should work fine too, maybe a dab of grease on the threads to keep 'em from sticking! Good Luck!

 

[Home Cookin']

Re: Plug for aluminum boat

I think I'd permanently seal that hole, and install a proper drain hole through the transom, at the bottom, for a rubber "crank plug" so you can run the water out. That's an important safety feature in my view, and a hole through the bottom is a major safety risk.

 

[JASinIL2006]

Re: Plug for aluminum boat

Yep, get a metal pipe plug and screw it in.

If you want, use a marine sealant, or JB Weld to secure it forever.

We had a habit of accidentally knocking the rubber plug out with our feet while fishing.
My dad JB Welded a plug in, back in the mid sixties, and the plug is still secure to this day.

Can make emptying the boat of rain water a bit of a hassle.

Our current boat has to be bailed, so we're used to emptying out rain water that's collected. Was the plug that you JB Welded a brass or bronze plug? No problem with it reacting with the aluminum?

Thanks!

 

[JASinIL2006]

Re: Plug for aluminum boat

I think I'd permanently seal that hole, and install a proper drain hole through the transom, at the bottom, for a rubber "crank plug" so you can run the water out. That's an important safety feature in my view, and a hole through the bottom is a major safety risk.

Yeah, the hole in the bottom of the boat makes me a bit nervous, too...

 

[roscoe]

Re: Plug for aluminum boat

Our current boat has to be bailed, so we're used to emptying out rain water that's collected. Was the plug that you JB Welded a brass or bronze plug? No problem with it reacting with the aluminum?

Thanks!

It is steel, possibly plated, hard to tell, its been there for over 40 years, and doesn't leak.

 

[smokeonthewater]

Re: Plug for aluminum boat

I think I'd permanently seal that hole, and install a proper drain hole through the transom, at the bottom, for a rubber "crank plug" so you can run the water out. That's an important safety feature in my view, and a hole through the bottom is a major safety risk.

Yeah, the hole in the bottom of the boat makes me a bit nervous, too...

.....If you look under the hole on the bottom of the boat there is likely a clamshell around it so that you can pull the plug while running at speed and drain any water in the boat.

A threaded plug in the bottom is NOT gonna spontaneously unscrew... It is not a safety risk at all..... again check, it MAY be able to function as a baler also.

 

[roscoe]

Re: Plug for aluminum boat

A threaded plug in the bottom is NOT gonna spontaneously unscrew... It is not a safety risk at all..... again check, it MAY be able to function as a baler also.

Agreed.
Our old Meyers has the self baler setup.

The problem was that dad would often kick the rubber plug out.
He would notice when his feet got wet.
The hole was not threaded.
He just screwed in the metal plug, and then used the JB Weld to hold it in place.


Since your hole is threaded, just screw in a plug and be done with it.

 

[Scott Danforth]

Re: Plug for aluminum boat

the bottom threaded hole is most likely a self bailer. it is either centered in the boat over the keel rib or it has a triangular plate covering the hole on the bottom, or its offset over one of the other bottom ribs.

This design is very common on many aluminum boats from the late 50's and 60's. as many have stated, screw the plug in and use the boat.

 

[JASinIL2006]

Re: Plug for aluminum boat

The hole does have some sort of plate riveted to the outside of the hull, with a cut-away over the back half of the plate. This is the self-baler, I presume? I don't have experience with these, but I'm guessing water would be sucked out if the plug was removed while the boat was at speed?

I'm not prejudiced against using the drain plug, really, my initial concern was about having two dissimilar metals (aluminum and something else) in contact and whether that would cause one metal to be corroded through galvanic reactions. It sounds like the general consensus is that a brass (or bronze or galvanized steel) plug will be fine, and I just just plug the darn boat and use it.

Yes?

 

[DuckHunterJon]

Re: Plug for aluminum boat

Yup, you got it.

 

[Home Cookin']

Re: Plug for aluminum boat

two things: however you plug it, you have to be able to remove the plug quickly so that you can bail out the boat. This is a safety issue. But equally as important, as someone mentioned, it has to be secure enough that it won't get kicked loose or something. That's why the better design is the plug against the transom.

if you haven't done this before, don't try to run out a large amount of water, as when you take off it will all run to the stern and if too much water, cause problems. Bail first. every boat must have a bailing device on board, especially those without bilges.

Technically, the boat is not "self bailing" because it will not drain the water sitting still. Boats with a deck above the waterline can have plugs or scuppers above the line, so that rain water drains out by gravity while the boat is moored. Some boats, like a 13' whaler, are self bailing with a small pull-start motor but not with a larger motor + battery. Yours has a drain plug, if you were describing it.

 

[smokeonthewater]

Re: Plug for aluminum boat

Don't use a galvanized steel or iron plug as the zink is a very thin coating and wears off.... use a brass or bronze plug. Screw it in with your fingers. If it comes out (it won't) you'll notice it right away... You won't sink. All you would have to do is put, the plug back in, stuff about anything in the hole, even a sock, put your foot on the hole, or simply start the engine and go.... The 4 foot geyser you see on popeye with the boat instantly going under just isn't reality.


Yes, that plug will allow the water to drain out if you remove it while running at speed.... It can actually drain it FASTER than a transom drain because the design makes a suction.

 

[smokeonthewater]

Re: Plug for aluminum boat

Actually, I have an orange nylon plug on my keychain that I've used a couple times when for whatever reason I got to the ramp and my plug wasn't in my door pocket. Snag a couple and ziptie the spare inside the boat.

http://www.iboats.com/Seasense-Nylo...0367249--**********.051760706--view_id.392237

This may just be the ultimate for you... no fear of corrosion, cheap, and easy to use without tools.

 

[steve49]

Re: Plug for aluminum boat

I have the same setup in my Sea Nymph, except it takes a 1/2 " plug. Any hardware store will have a brass plug to fit that drain. I've had the boat for 12 yrs. and it stays in salt water all the time down here in FL. No corrosion problems at all.

 

[JASinIL2006]

Re: Plug for aluminum boat

I have the same setup in my Sea Nymph, except it takes a 1/2 " plug. Any hardware store will have a brass plug to fit that drain. I've had the boat for 12 yrs. and it stays in salt water all the time down here in FL. No corrosion problems at all.

Good to know. I guess I'll just buy brass plug or two (so I have a backup) and not worry about it.

Thanks to everyone for your help! This board has been a great resource as I'm getting into boating! You all are great!