Don’t ignore above-the-water-line thru hulls!

Jan 7, 2011
4,727
Oday 322 East Chicago, IN
I have been meaning to tackle this job for a while (6 years since a surveyor mentioned it on my pre-purchase survey).

The small one on the right is the drain from the propane locker. It came out intact.

The one on the left is for the bilge pump hose,.. the head broke off :yikes: when I was trying to get the hose off the barb! I hope this is the one the surveyor noted was cracked! The rest of the damage came from me using the piece to try to drive out a piece stuck in the hull.

The large one in the middle is a scupper drain. It came out ok, but the head is very brittle and pieces broke off as I was trying to pry it out of the hull.

My boat is 30 years old, and since there was blue paint that matches the inside of the hull, I am assuming that these are all original.

These are all “above the water line”, but several of them are under water when motoring and the boat squats in the water.

I am making a list of new parts (8 plastic thru hulls in total, 4 different sizes). Next up, checking the hoses that connect to these...I know the propane locker drain hoses (2 of them) are in bad shape.

306AEACF-E368-4658-8EDC-A029BB06C6EE.jpeg


It was almost 50 degrees today in Chicago area, so a good day to start a project ;-)

Cheers,

Greg
 

Tom J

.
Sep 30, 2008
2,301
Catalina 310 Quincy, MA
Good reminder, thanks. I've had this issue with a couple of outboard boats in the past. My anchor locker drains through a hose to a similar through hull, and I do check both every season.
 

NYSail

.
Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
Sure you know this but when replacing get the marelon fittings not just the cheap plastic. UV kills the above water line fittings. It’s one of my projects for next year.

good luck
Greg
 
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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
My anchor locker drains through a hose to a similar through hull, and I do check both every season.
Put a second drain in the anchor locker, maybe 2 inches higher and on the other side in case the OEM gets clogged.
 
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Apr 8, 2010
1,942
Ericson Yachts Olson 34 28400 Portland OR
I replaced our above-water thruhulls with SS fittings. Marlon would have been just fine also.
Those old cast plastic fittings were attacked by UV, and a ton of builders in the 80's put them into a ton of sailboats and powerboats.
It is a bit disconcerting to see a row or 6 or 8 of them down the side of a Bayliner, just an inch or two above the 'light load' waterline.
 
Last edited:
Jan 19, 2010
1,169
Catalina 34 Casco Bay
The NOW owner of our former O'Day called me one day in a panic. He decided to replace his cockpit drain thru hulls....while in the water ! He was surprised, surprised I tell you to see the water so close. He was lucky. the boat was in a slip on a river so very little movement. Wanted advice. Told him to gorilla tape over the hole and make arrangements to have the boat lifted. $$$$ He could have done this during the winter lay up on the hard... DOH !
 
Sep 25, 2008
957
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
Wouldn't have any thru hulls that aren't ss or bronze on my boat.......above or below the waterline!
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
Stainless steel hull fittings look classy :cool:

I'm in the process of replacing PVC fittings attached to any thru hull valves with bronze Groco fittings.
 
Jan 7, 2011
4,727
Oday 322 East Chicago, IN
The NOW owner of our former O'Day called me one day in a panic. He decided to replace his cockpit drain thru hulls....while in the water ! He was surprised, surprised I tell you to see the water so close. He was lucky. the boat was in a slip on a river so very little movement. Wanted advice. Told him to gorilla tape over the hole and make arrangements to have the boat lifted. $$$$ He could have done this during the winter lay up on the hard... DOH !
My son was doing a video with his GoPro when we were out for a sail...still motoring when he put the camera under the water and filmed the prop...and I noticed the scupper drains completely under water...and the bilge thru hulls also under water...and these are above the water line fittings.

the day I hauled out, I was draining the water heater before hitting the travel lift...I usually pull the hose off the scupper drain and run the water heater drain line out the hole....water was awfully close to the hole.

So, I figured winter layup was the best time to tackle this.

Greg
 
Jan 19, 2010
1,169
Catalina 34 Casco Bay
My son was doing a video with his GoPro when we were out for a sail...still motoring when he put the camera under the water and filmed the prop...and I noticed the scupper drains completely under water...and the bilge thru hulls also under water...and these are above the water line fittings.

the day I hauled out, I was draining the water heater before hitting the travel lift...I usually pull the hose off the scupper drain and run the water heater drain line out the hole....water was awfully close to the hole.

So, I figured winter layup was the best time to tackle this.

Greg
When heeled on a starboard tack, both of my bilge thru hulls are submerged. Both have check valves though.
 

Tom J

.
Sep 30, 2008
2,301
Catalina 310 Quincy, MA
When heeled on a starboard tack, both of my bilge thru hulls are submerged. Both have check valves though.
I have come to appreciate Gerry Douglas' design of the C310 more and more. The cockpit is self draining, so no scuppers, and the bilge through hulls are located just under the hull/deck joint.
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
The SS capped fittings are better than plain nylon or plastic because the SS blocks damaging UV. However, I would still prefer to use bronze, chrome plated bronze or SS. Doing this adds expense, however, there are some places some extra expense is warranted.
 
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Jan 7, 2011
4,727
Oday 322 East Chicago, IN
Thanks for all the input.

Does this site sell Sikaflex or Boatlife caulk? I searched, but no joy ;-(

Greg
 
Jun 1, 2007
265
O'Day 322 Mt.Sinai
I have been meaning to tackle this job for a while (6 years since a surveyor mentioned it on my pre-purchase survey).

The small one on the right is the drain from the propane locker. It came out intact.

The one on the left is for the bilge pump hose,.. the head broke off :yikes: when I was trying to get the hose off the barb! I hope this is the one the surveyor noted was cracked! The rest of the damage came from me using the piece to try to drive out a piece stuck in the hull.

The large one in the middle is a scupper drain. It came out ok, but the head is very brittle and pieces broke off as I was trying to pry it out of the hull.

My boat is 30 years old, and since there was blue paint that matches the inside of the hull, I am assuming that these are all original.

These are all “above the water line”, but several of them are under water when motoring and the boat squats in the water.

I am making a list of new parts (8 plastic thru hulls in total, 4 different sizes). Next up, checking the hoses that connect to these...I know the propane locker drain hoses (2 of them) are in bad shape.

View attachment 188060

It was almost 50 degrees today in Chicago area, so a good day to start a project ;-)

Cheers,

Greg
Ugh.. Like I don't have enough on my plate this winter? :)
 
Jan 7, 2011
4,727
Oday 322 East Chicago, IN
Ugh.. Like I don't have enough on my plate this winter? :)
Yep...

The good news is I only have 3 below the waterline thru-hull in the boat...they don’t look bad, but will have them on the list soon. Of course that doesn’t include transducers :facepalm:

Greg
 
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