Bilge Drain Question

Pusher

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Why do they put the drain through the transom instead of thivkening the hull and go strain down? had For someone who wouldn't run the boat and pull the drain if they hwter in the bilge it seems like an opertunity for a rotten transom.

Just curious.
 

southkogs

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I surely don't know the specific reason (or even all of 'em), but one I know is - if your plug comes out while you're away from shore, and you can get the boat moving - especially up on plane - the water will drain until you come to a rest again. I had to do that one time. Saw water pouring in, realized the plug came out - popped the engine on and climbed up on plane to drain the water out.

I didn't go all the way back to the dock. Powered down, turned the bilge on and dove in with a spare plug.
 

H20Rat

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Most boat plugs go in from the outside, that is actually preferable anyway since the water pressure is pushing it in, instead of trying to push it out. Having an exterior plug on the bottom of the boat is all kinds of bad news.

(lots of wake-boats have ballast drain tanks that have an interior mounted drain plug that goes out the bottom, so it is done for specific cases)
 

roffey

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As kids we would pull the plug intentionally in my father small fishing boat. We would see how much water we could take on before the boat would not plane. You would be amazed how much water can be in the bottom of a boat and still be operational. Not sure if I should tell you people the stuff I did to a boat as teenager. I only had access to a 9.9 12 foot fishing boat, thank god.
 

jbcurt00

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To work optimally, there would have to be a directional cup on the hull bottom facing the stern to create a sucking venturi to pull water out of the hull and thru a down facing hole. Amd the plug wpuld be on the inside, where it someone mentioned wate pressure is working against you, at rest.

Lots of vintage tin and glass boats have this pod on the bottom of the hull.

It sticks down, and can be damaged or in the way on the trailer or beached....


Sticking down it also creates drag and turbulence below the hull.

Lost favor w manufacturers.

I had a 1960 Glaspar G3 for about 10min, and it had a long handled bilge plug apparatus (original to the boat, dealer added?) that was spring loaded to maintain pressure against the transom.

From the helm (its a short 13ft boat) you could turn 1/2way around and reach the handle. Push in and turn the handle from 3 oclock, down to 6 oclock and the bilge hole wss plugged. Push in and reverse, and the plug was out of the hole enough to let water drain out the back.

Neat feature and handy to have/use, but lots of moving parts compared to a flip or screw type plug and awkward for whoever was sitting behind the captain to have poking out beside (into?) their back... Ever now and then I see a similar setup for sale on ebay..
 

H20Rat

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As kids we would pull the plug intentionally in my father small fishing boat. We would see how much water we could take on before the boat would not plane. You would be amazed how much water can be in the bottom of a boat and still be operational. Not sure if I should tell you people the stuff I did to a boat as teenager. I only had access to a 9.9 12 foot fishing boat, thank god.

I did the same growing up with my 15.5 ft tri-hull... It was my wakeboat for wakeboarding, and you could actually get a surprisingly large wake if you had enough water in the bottom of the hull.
 

JimS123

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Ever hear of a Garboard Plug? The Garboard plank is the first plank on the bottom of the boat next to the keel. Back in the day most boats had a Garboard Plug, which was on the bottom of the boat. The plug was installed from the inside, thus no turbulence or other issues on the outside. Today they still sell "Garboard Plugs", but almost nobody knows where they belong. I don't know if the transom is the best place for the plug, but its probably the most convenient.
 

roffey

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to be honest I thought a garboard plug was just the plug in the back of the boat. I unscrew it when the boat is on the trailer?
 

Alumarine

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I didn't realize that was called a garboard.
My Alumarine had one. It drained out the bottom and had a clamshell around the drain hole with the opening facing the stern.
It was a royal pain to get at the plug the way the rear storage was configured.
 

Pusher

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Wow, I bet everyone can tell I typed that on the way out the door this morning! Sorry guys.

Very interesting. I'll have to look into this garboard plug thru-hull setup. I haven't actually heard of it before. Good feedback and stories guys, thank you.
 

Scott Danforth

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Its in the back because its eazy for the boat manufacturers to put it there. They are at the back of the boat drilling holes for motors, cleats, swim stairs, etc.

Not cost effective to shimmy a worker under a hull.

That coupled with the desire for boats to have a finite life so they can continue to make and sell boats means that the plug is in back where it is cheap and eazy to put it
 
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JimS123

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Its in the back because its eazy for the boat manufacturers to put it there. They are at the back of the boat drilling holes for motors, cleats, swim stairs, etc.

Not cost effective to shimmy a worker under a hull.

That coupled with the desire for boats to have a finite life so they can continue to make and sell boats means that the plug is in back where it is cheap and eazy to put it
Back when boats were wood and actually HAD a Garboard plank, the hulls were built keel-up (bottom up), so drilling the drain hole was done from the top, no crawling underneath. Of course, at that time it would have been just as easy to drill the transom.

What I can say, though, is that my tinnies and FG boats with transom plugs always leave a little water in the bilge because the plug is slightly above the bottom. OTOH, my woodie with the Garboard plug drains every last drop.
 

Pusher

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That's exactly where I was coming from guys. Seems like a crock building something that you know is going to rot out.

I'm thinking if I redo my transom I'll put the garbourd facing skyward in the bilge and a horseshoe shaped backing plate on the bottom facing the transom.

Worst case scenario, I run aground and grind the aluminum backing plate down instead of the fiberglass.
 

Baylinerchuck

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The drain plug on my Chap is actually below the transom wood by about 2". The hole is through the fiberglass only. Might very well be the only well thought out design feature for longevity in the whole cotton pickin boat. Lol.
 

fhhuber

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One simple reason to put the drain plug hole low on the transom:

When the boat is stored on the trailer you can just raise the nose and the drain is then the lowest point, so all the water goes out.

Then its a matter of preventing the hole from being plugged by leaves and trash while the boat is parked.

You can drill the hole oversize so you can epoxy in a stub of thin wall aluminum tube and you will have dealt with the issue of the exposed wood due to the hole being drilled through the transom.
 

JoLin

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My boat has a through-hull drain about 4 feet forward of the transom. Could never get all the water out when the boat was blocked for the winter because it wasn't absolutely level. Two years ago I drilled and installed a new drain in the transom. I have the transporter block the boat bow high (4-6 inches). Now I know I'm getting it all out of there.

fhhuber's method of installation is good, but I wouldn't use aluminum on a boat that's slipped in salt all season. I drilled the hole a little oversize and lined it with epoxy before I installed the plug with lots of 5200.

My .02
 

JimS123

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That's exactly where I was coming from guys. Seems like a crock building something that you know is going to rot out.

I'm thinking if I redo my transom I'll put the garbourd facing skyward in the bilge and a horseshoe shaped backing plate on the bottom facing the transom.

Worst case scenario, I run aground and grind the aluminum backing plate down instead of the fiberglass.
My guess is that no transom ever rotted out because of a factory installed drain plug. They rot because the owner doesn't remove the plug and lets water sit in the bilge.
 

Pusher

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I thought the same until winter tore a hole through my tarp and the drain hole froze up. Nothing that the other setup would have fixed though.

I waz thinking since there's little to no support priceded in the lower two inches of a transom ou could lay a 3" stretch of transom donw fiberglassed in, then your main transom on top of that. It would help keep rot at bay between the two.
 

hal2814

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My current boat is an old Ski Nautique. It's an inboard and the drain plug is right in the middle of the boat under the engine. A lot of non-v-drive inboards are set up this way. I'd personally prefer a rear plug. When my boat is trailered, I have to be careful that it's sitting relatively level and even then water has a tendency to pool either in the front or back. I never had that problem with a rear drain. I just parked it bow high and all of the water drained out the back. As far as rot goes, a lot of v-drives have rear plugs and they don't have a lot of issues with transom rot. I'm guessing the force being exerted on the transom by outboards and outdrives is a bigger factor in transom rot than the drain hole.
 

Alumarine

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I waz thinking since there's little to no support priceded in the lower two inches of a transom ou could lay a 3" stretch of transom donw fiberglassed in, then your main transom on top of that. It would help keep rot at bay between the two.

On my aluminum boats the wood part of the transom is 3" - 4" above the hull with the drain plug between the transom and the hull.
Even with a lot of water in the bilge it won't touch the wood.
Doesn't help if water gets and stays above that though.
 
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