Duncanson 35 pressurised salt water in fresh water tanks below waterline

[Hop2]

Hi All, I'm looking for any advice or knowledge, I recently bought a fibreglass Duncanson 35 (around 1976) in need of some work (the previous owner told me it was only cosmetic required and he had a survey that seemed a little too positive, anyway, the price was low and he had a lot of interest so I went for it - there aren't many boats like this around atm). It's on a swing mooring in Brisbane waters (Gosford). I'm slowly checking out all the boat systems, and starting to think/realise there is something more serious wrong. There are two large tanks under the floor on either side of the keel attachment. When I take the cap off one of the tanks (I think these are meant to be fresh water tanks, they look like they are fibreglass and built into the boat during construction) salty water comes gushing in to the bilge. The other cap produces a flow of salty water too, but not nearly as high a flow rate. There is an automatic bilge pump, but it seems like the water tank cap, and any other connections to the tanks (that may not be designed for any pressure) are currently critical in preventing the boat from sinking. It seems to me that salt water must be getting through the hull into these tanks, suggesting hull damage? Is anyone familiar with this design? Does this sound likely? Could it be anything else?

I'm thinking I should get the boat out of the water ASAP, but I'm not familiar with the area. Can anyone recommend somewhere to take it around Gosford? I'm guessing it will likely need to be out of the water for a while? It there anything I can/should do while on the mooring?

Thanks very much for any advice!
Liam

[Bruce K]

Booker Bay Marina or Machans Marina, next to each other, just south of the Rip Bridge.

[Spot]

Hello Liam, welcome to CF.
My first guess is that they are abandoned through-hull fittings.
Perusing the interwebs, it seems some Duncanson's had fuel tanks in bilge and fresh water below the saloon seats. Where do the green garden hoses lead to/from?
Sorry I cannot help with anything more specific to the boat or your area in AUS. Getting hauled out and making your own survey/ to-do list seems like a good idea.

[Hop2]

Thanks for the reply, Spot, I would be very glad if you are right, because that would suggest my first guess is wrong. I thought you would put something more sturdy than these plastic caps on an abandoned thru hull? But I have little experience here, so hopefully I was wrong. The previous guy did say something about the diesel originally being under the floor, but someone before him moved it higher (into the aft berth) to get gravity assist. The garden hoses seem to go - one to an electric pump and one to a foot pump into the galley sink. Neither are working , but the foot pump sounds like it is sucking air (not sea water, another good sign?). I didnt work out where they are coming from, two seem to disappear into the bilge water (maybe they turn right under there into a tank that could be under the starboard berth, the 3rd one might be delivering water to the shower on the other side.

Thanks very much for your opinion. I really appreciate the guidance! Hopefully this isn't as serious as I feared, but I agree about a survey so I have a better idea where I am starting from.

[Hop2]

Great, thanks Bruce! Much appreciated

[Searles]

Those are through hull fittings for instrument se senders ,nothing to do with fw tanks ,yes some of the duncos had built in tanks , most had ss water and fuel tanks ,good boat to windward not so good of the wind by modern standards .⛵️⚓️

[Hop2]

Originally Posted by Searles

Those are through hull fittings for instrument se senders ,nothing to do with fw tanks ,yes some of the duncos had built in tanks , most had ss water and fuel tanks ,good boat to windward not so good of the wind by modern standards .⛵️⚓️

Thanks Searles! In my defence I'm pretty sure the guy selling the boat said there was about 300L of fresh water was under the floor, but as I study pictures of other dunc 35s out of the water I realise there is no doubt you and Spot are right. There is no space for tanks on the other side of those holes. Its very reassuring to hear from people who know.

[Ard Righ]

Hi, I also own a Duncanson 35. I cannot speculate what your problem is, but hope this may help. On my boat the fresh water tanks are built into the hull either side of the keel under the settees. The fuel tank is in the bilge forward of a bulkhead about midships. The aft end of this is visible when you open the big floor hatch in the saloon. There should be no connection to the sea from the fresh water tanks or (obviously) the fuel tank. All tanks are accessed via a small filler in the top. I had to remove a table in the cabin to get at the floor to access the inspection plate on the fuel tank, but the water tanks do not have an opening that gives easy access. All I can suggest is clear the bilge water completely and follow each hose to its end. The water tank breathers ended up in the forward end of each of the settee berths and the fuel tank breather is in the space at the forward end of the table.

My boat has two foot pumps. One for fresh water to the sink and one for salt water also to the sink. The through hull for the salt water is in the cupboard aft of the stove. There is no direct connection to the water tanks from the salt water inlet so the risk of contaminating the fresh water is very unlikely.

[wingssail]

Originally Posted by Searles

Those are through hull fittings for instrument se senders ,nothing to do with fw tanks ,yes some of the duncos had built in tanks , most had ss water and fuel tanks ,good boat to windward not so good of the wind by modern standards .⛵️⚓️

Yes, Those look exactly like early B&G Speedo housings. There are two because B&G had provision for using one speedometer paddle wheel on one tack, and the other on the other tack.

[psk125]

To confirm Spot's logical suggestion it should be easy to take a quick swim and have a look at the hull along the turn of the bilge and see if there are openings for through-hulls there, port and starboard. From the inside it looks like he's right.