Inner Hull Drain 235cc

Offshoreman

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Here is a brief tutorial on installing an inner hull drain in the Triumph Boats 235cc:

On the transom, locate and mark a spot 3.5 inches left (port) of the center line of the hull (along the dead rise), and 2.25 inches up (90 degrees to the dead rise) and drill a small pilot hole. Stand by for water to come out! After it drains, use the pilot hole as a guide to drill a 1-inch hole. (The angle of the attached photo makes the holes look like different diameters, both are 1").

Clean everything and remove some of the inner hull foam to make room for the drain. Run the 1" drill bit in and work out some of the foam. I am using a garboard drain (image) with a captured drain plug, so it requires a bit more space, so I removed a bit more foam. It looks as if the hole you just drilled is above the bilge drain, and it is, but it is in the inner hull. It is the lowest point in the inner hull. The bilge drain is in a different compartment.

In the photo depicting a cross section of the hull (you're looking aft), the location for the inner hull drain is the triangular shaped area to the right and left of the "V" shaped structure. I chose to go left (port), but you could choose to mount one to the right (starboard). That "V" shaped structure separates the open bilge from the inner hull, and it creates the open space between the bilge where your bilge pump is, and the bilge drain plug at the transom. Use only Elastomeric adhesive and install the new drain.
 

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Offshoreman

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A simple list of tools to get this job done right: Hopefully in order of use....

Tape measure.
A small square to get the 2.25 inch measurement in just the right place.
(use the square to double check your measurements).
Sharpie (to mark "the spot").
Drill (I prefer a cordless).
1/4 drill bit (pilot hole).
1 inch drill bit (final hole). ***If the drain plug you use requires a different size hole, use that size drill bit***
Long flat screwdriver to dig out some foam.
A good drain plug. Your choice of stainless, brass or plastic. I do not recommend plastic.
Mock up the drain plug to get the screw holes located.
Sharpie again to mark the screw holes.
1/8 inch drill bit (for the drain plug screw holes).
Elastomeric (Sudbury if you can't find Rule).
Place the drain in place in a bed of Elastomeric.
Phillips screw driver (snug down drain plug screws).

I recommend stainless screws with a stainless drain, and brass screws with a brass drain. Stainless screws with a plastic drain.

Make sure you read the Elastomeric label so you give sufficient time for the adhesive to cure.
 

Stormi

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Premium Member
City
San Diego
A simple list of tools to get this job done right: Hopefully in order of use....

Tape measure.
A small square to get the 2.25 inch measurement in just the right place.
(use the square to double check your measurements).
Sharpie (to mark "the spot").
Drill (I prefer a cordless).
1/4 drill bit (pilot hole).
1 inch drill bit (final hole). ***If the drain plug you use requires a different size hole, use that size drill bit***
Long flat screwdriver to dig out some foam.
A good drain plug. Your choice of stainless, brass or plastic. I do not recommend plastic.
Mock up the drain plug to get the screw holes located.
Sharpie again to mark the screw holes.
1/8 inch drill bit (for the drain plug screw holes).
Elastomeric (Sudbury if you can't find Rule).
Place the drain in place in a bed of Elastomeric.
Phillips screw driver (snug down drain plug screws).

I recommend stainless screws with a stainless drain, and brass screws with a brass drain. Stainless screws with a plastic drain.

Make sure you read the Elastomeric label so you give sufficient time for the adhesive to cure.
 

Stormi

Participating Member
Premium Member
City
San Diego
Did you have a lot of water coming out of the new inner hull drain?
I added holes last winter in the bilge area liked you recommended and had almost no water coming out of it.
Seeems to me my inner hull is very dry.
 

Offshoreman

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I had only an occasional drip from the drains I put in the Bilge area. I got about 1.5 gallons out of the transom drain I just installed. Now it's also just a very slow drip. Happy to know I'm not water logged.
 

Offshoreman

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Here's a photo of the moment the drill bit initially pierced the transom.
 

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Offshoreman

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I only did one side. I don't think it matters which side. It's all one compartment.
 

Offshoreman

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I suppose a small amount of water could remain below the drain that you install, but I think it would be an insignificant amount.
 

Offshoreman

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I went ahead and opened the starboard side of the inner hull area to see if water was any pooling there. I'v been uncertain if the inner hull areas are truly connected there or not. So, I drilled and exploratory hole and found water, thought it was not pouring out like it did when I installed the port side inner hull drain. Rather than sealing the hole up, I went ahead and put in a second drain. I used the same process as above, and installed the same type of drain. The foam was dripping wet when it was drilled out of the hole. Overnight and it has only dripped a little.

I pulled the plug on the port side inner hull drain and ran my little finger up in there. The foam felt dry. My suspicions must be correct that the inner hull is one large void throughout the boat, but that the voids have separations near the transom where water can pool.
 

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Dave_L1

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Florida
Great Info with pictures for this hull so I "Stuck It" ;)

Thanks Martin!
 

JoeRocket

Registered Member
Here is a brief tutorial on installing an inner hull drain in the Triumph Boats 235cc:

On the transom, locate and mark a spot 3.5 inches left (port) of the center line of the hull (along the dead rise), and 2.25 inches up (90 degrees to the dead rise) and drill a small pilot hole. Stand by for water to come out! After it drains, use the pilot hole as a guide to drill a 1-inch hole. (The angle of the attached photo makes the holes look like different diameters, both are 1").

Clean everything and remove some of the inner hull foam to make room for the drain. Run the 1" drill bit in and work out some of the foam. I am using a garboard drain (image) with a captured drain plug, so it requires a bit more space, so I removed a bit more foam. It looks as if the hole you just drilled is above the bilge drain, and it is, but it is in the inner hull. It is the lowest point in the inner hull. The bilge drain is in a different compartment.

In the photo depicting a cross section of the hull (you're looking aft), the location for the inner hull drain is the triangular shaped area to the right and left of the "V" shaped structure. I chose to go left (port), but you could choose to mount one to the right (starboard). That "V" shaped structure separates the open bilge from the inner hull, and it creates the open space between the bilge where your bilge pump is, and the bilge drain plug at the transom. Use only Elastomeric adhesive and install the new drain.
Where did you get the cross section picture of the 235 hull?
 

Offshoreman

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Right here on Performance Outdoors! One of the members is a former Triumph Boat engineer.
 

Offshoreman

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Also, I have removed the drain plugs and replaced them with a standard style drain. They just wouldn't hold a seal. They were allowing water in through their inferior seal. Photo to follow....


Despite a clean install, proper application of elastomeric, etc., etc., they leaked allowing water INTO the hull and inner hull.

So, here's what I changed them to:

Plug

Ok, I removed the plugs and cleaned the area by removing all adhesive, then used 409 and some alcohol. Clean and dry.... I made sure the new plugs were going to fit the holes, then mocked them into place and marked the new screw holes. I drilled small pilot holes with a 1/8" drill bit.

I took a small torch and just flashed the area. It has a smoothing effect on the roplene, it warmed it up a little and made sure it was completely dry.

Then I prepped the area with 3M94 primer. Once the primer was set up, I applied a good deal of clear Sudbury Elastomeric to the drains, and a small amount to the hull and previous screw holes and installed them with stainless screws. Much of the excess elastomeric squished out as you can see in the photo.

I like to apply toilet bowl gasket wax (bees wax I suppose) to the threads of the drain plugs. It ensures they will never seize in place and add a degree of water tightness. Hhmm, is that even a word?

I had the boat in the water a few days ago for several hours when my wife and I launched and went to the local marina for dinner. When we got home and pulled the plugs, no more water.....

Now, I just need to trim off the excess to make it look better. That's something I frequently see; use of adhesive, it squishes out from around a new fitting and rather than let it set up and cure then remove it cleanly, I've seen people try to smear it away when it's still wet. Let it cure and use a small razor blade, it will be sweet.
 

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Manomet

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Manomet
Nice writeup. Thank you. I've been wondering about water in my hull. Will do same in the spring and post results.
 

Offshoreman

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Update: I left the boat in the water at the marina for three days and NO WATER from the inner hull drains. The new fittings work perfect.
 

JoeRocket

Registered Member
Hey guys I wanted to let everyone know that I completed this procedure exactly as described in the second revision, to include flaming it with a torch, 3M94 prime,r brass Garlock drains with toilette bowl wax, and elastomeric sealant.
My boat was in the water for 6-8 weeks with near constant use, when I finally pulled it out and drained the inner hull about one cup of water came out.
Compared to about two gallons drained when I initially pierced the hull.
If you want to put the inner hull drains in your boat this is the way to do it!
I had to carefully sand off the bottom paint in the area, and I didn't install any extra drains in the bilge area on the inside of the boat. 20190220_184517.jpg
 

Offshoreman

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Very Good!!
 

Stafford1969

Registered Member
State
florida
How much water can the inner hull hold? I have a 2008 235 and its nickname is "the crooked cruiser." Constantly leaning left and right to the point you can't control it. Very slow coming out of the hole, and top speed 32mph. Wondering if the inner hull is my problem.
 
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