Drain Plug on Aluminum Boat


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Jul 28, 2008
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I need some help on replacing a drain plug on an old aluminum boat that I bought. It appears to be a 1" diameter hole in the BOTTOM, that tapers in. Since the boat's hull is only +/- 1/8" thick......what are my options? I'm reluctant to replace it with an expandable rubber plug as it's around 2" long and will stick out the bottom of the boat.

Any help is appreciated.

Forgot to add the threads in the hole are pretty mangled.

Thanks for the replies. I did purchase a "one-way" garboard plug. However, it stuck out the bottom of the boat around 1-1/2". In my opinion...that protrudes too far. From the looks of this drain plug.....does anyone thing this came with the boat or something added after? I will look into the aluminum disc procedure...sounds like the best idea I've heard so far.

Thanks again,


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I had a Cherokee that had a hole like that. It came with the factory aluminum plug, which had shallow threads, and then a flange with a gasket at the top. Doubt you you could find anything aftermarket that would be as ideal as that was. I also at one point had an old Larson that was a pond boat, that had a similar plug, just 1/2 inch diameter. Because it never operated over trolling motor speeds, we just had a brass plug and teflon tape in it.

You could unbolt that little backwards scoop underneath, and use those same holes for your patch.
looks to me that you can go your local autoparts store and use one of the small expansion plugs that are replacement for freeze plugs you can take it out and put it back in with just a wrench
Thanks for the help. I'll try some of the suggestions.

If all else fails, I patch over it and add one in the transom.

I appreciate your help!

Agree with the others, lots of 1” expandable plugs that won’t protrude a whole lot. The plug is near the transom and your motor would hit bottom long before the plug would.
I'd be tempted to patch the bottom up and install a plug in the transom. I understand your apprehension in having it stick out the bottom. Since something must be done, I'd move the dang thing.
till has the most popular solution.

The Crestliner product typically works as these were common across many brands of boats.
Previously known as a wet transom garboard drain, they originally came with a tall handle or even a spring-loaded handle that enabled bailing while under way. (Why they're in the floor)
Perko was another common vendor but the modern machined plugs are great solutions as we now have bilge pumps.

Beware there are two common diameters with different thread pitches. Usually it's a 3/4 npt, but 5/8 are out there, too.

Edit: I see now you've mentioned a 1" diameter. I have to admit I'm unaware of that size machined plug. I've heard of folks using the npt-threaded plugs from food barrels, though.
As Thill pointed out ~this is an old post, I'm pretty sure he either got it fixed or sold the boat - it's only been almost 16 years.
My old, 1987 Crestliner had the same plug, 1" diameter, with that scoop deflector/cup in front of it. Nice that they still make them.