Why does a boat have a drain plug?

[davismwfl]

Ok, so I admit, I started boating a little strangely. I went from friends smaller boats growing up to my own 1969 28' Owens sport fisher, which was an inboard and 10ft beam. No drain plug, just an inboard with a shaft seal I replaced for a dry version after packing it a couple of times.

So bringing me to today, I have a 1995 250DA Sundancer and it has a drain plug that I have to be very aware of. I sorta understand since it is a trailerable boat that the drain plug lets water that gets in a boat exit. After all I learned there is not such thing as a dry boat. But why a drain plug? What is the engineering reason versus just a bilge pump like my sport fisher had? The only way water got out of the bilge was us pumping it out with the sport fisher. Is the drain plug just convenience?

I fully admit ignorance here, but I am an engineer and like to understand the reasons not just the results. I can come up with lots of hypothesis for the drain plug, but I am curious as to the real reason that maybe I am either overthinking or just missing.

 

[NotHerDecision]

My simple guess is it allows all the water to drain out at the ramp when the boat is at a steep incline. Bilge pumps just never remove all the water so I see a drain plus as a great option on a trailerable boat. Think about using it during below freezing weather, you really need to fully drain the boat.


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[Bridog]

Bilge pumps are not an option on boats stored for several months during the winter. Need another way for water to exit.

 

[PMC]

I don't have a garboard plug and have a winter layup in freezing temps when the boat is on land. I have to winterize the bilge pumps, and leave antifreeze in the bilge just incase rain water finds its way in. The obvious benifit is not having a hole through the transom to worry about water intrusion .

 

[Westie]

I don't have a garboard drain plug on my boat. In fact I don't even have a garboard on my boat.
I do however have a transom drain plug.
On a trailer boat in BC, Alberta, Saskatchewan, Montana, Idaho, Washington and Oregon it's actually illegal to have your boat on the highway with the drain plug in. This is to ensure the bilge doesn't have any water in it that may spread invasive species, particular zebra mussels. They do have checks on the highways and even have a sniffer dog looking for them.

With just a bilge pump there is no way you are going to get all the water out of the bilge.

 

[davismwfl]

Interesting. The freezing issue hadn't dawned on me but makes sense. And the transfer of species is interesting but also makes a lot of sense.

I do like the ease it gives in getting a fairly dry bilge. But I am also floored by the number of times this item causes issues for people. And it just seems foreign to me to intentionally have a hole you need to plug.

Thanks for for the insights.

 

[hottoddie]

My 390 has a drain plug and I leave it out during winter storage even thou the boat is shrink wrapped. If a winter storm were to destroy the shrink wrap and soak the boat with water at least the water would escape the boat thru the drain plug. Keep in mind that "A BOAT IS DESIGNED TO BE IN THE WATER, NOT FULL OF WATER"

 

[BillK2632]

Plenty of boats have "sunk on their trailer", always leave the plug out if the boat is stored outside on a trailer. It is amazing how much water can end up in the boat from raining pooling up and collapsing a cover. Occasionally I pull my plug and have the lift driver tilt the boat up, usually close to a gallon drains out that the bilge pump doesn't pick up.

 

[skibum]

I was at a marina in Maryland where they had a large trawler sitting on stands on land waiting for it's Canadian owners to come finish working on it so they could take it home. It was uncovered. Over the course of the spring and summer, the rain had managed to fill the hull with over 3' of water. The marina did not have the keys, and no one was inspecting it on a regular basis. The marina employee was telling me that when the couple arrived to "finish up" work on the boat that they found it "sunk on land". The engine was flooded and there was major damage to everything down below deck. The insurance company declared it a total loss. Apparently, they were relying on the bilge pumps to keep her dry, but their battery chargers had died. I don't think that boat even had a drain plug.

 

[KevinC]

My 390 has a drain plug and I leave it out during winter storage even thou the boat is shrink wrapped. If a winter storm were to destroy the shrink wrap and soak the boat with water at least the water would escape the boat thru the drain plug. Keep in mind that "A BOAT IS DESIGNED TO BE IN THE WATER, NOT FULL OF WATER"

Unfortunately Hurricane Sandy destroyed a lot of boats on LI that were stored with the drain plugs out. As the water rose the bilges filled and in essence sunk then boats where they were blocked in storage. Those with plugs in floated and in some cases suffered less damage - so it is something to be mindfull of depending on your situation.

-Kevin