2556 - So many thru-hulls-gctid804088

[Solandri]

I bought a 1994 2556 in January, and have finally gotten some time to work on fixing it up. They survey recommended replacing the plastic thru-hulls. So I tried tugging on one of the hoses under the cockpit to see how bad it was. The thru-hull snapped right off. Okay... glad that happened while I was testing and not on the water. I've ordered a bunch of new thru-hulls (chrome-plated bronze $$). But I figured this would be a good time to learn what the heck all these thru-hulls are for. Based on pictures I can find online, the thru-hulls seem to be fairly consistent for the 1991-1994 models.

Starting from the left of this picture of the starboard side:

[img size=800]http://solandri.com/misc/IMG_7005.jpg[/img]

S1 - plastic 3/4". I'm guessing the bilge? Hose goes underneath engine.

S2 - plastic 3/4". Hot water tank? Hose goes behind holding tank.

S3 - plastic 1". Holding tank vent.

S4 - plastic 3/4". Water tank? Hose goes behind holding tank.

S5 - metal. Fuel tank vent?

S6 - plastic 3/4". Head sink drain

S7 - metal. Another fuel tank vent?

S8 - (not in picture) plastic 1 3/8" (not exactly sure of size). Galley sink drain

S9 - (not in picture) plastic 3/4". Anchor locker drain.

Port side (not pictured - only one)

P1 - plastic 3/4". Leads to pump underneath the under-dinette berth. I'm guessing this is for a bilge amidships?

Does anyone know for sure what S1, S2, S4, and P1 are?

Are both S5 and S7 fuel tank vents?

How do you access the S8 thru-hull? I can see it's for the galley sink drain, but the cabinetry totally blocks my ability to reach or crawl in far enough to access it from the inside. Maybe remove the stove to access it from above?

Also, there are four cockpit drains which lead to scuppers on the transom. Should I consider replacing these too?

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Edit: Summary of answers for future reference.

S1 - plastic 3/4". Bilge pump.

S2 - plastic 3/4". Fish locker drain (older models), flybridge drain (newer models).

S3 - plastic 1". Holding tank macerator.

S4 - plastic 3/4". Shower sump.

S5 - meta vent. Holding tank vent. (Recommended to replace with open marelon vent).

S6 - plastic 3/4". Head sink drain

S7 - metal vent. Fresh water tank vent.

S8 - plastic 1 1/2". Galley sink drain

S9 - (not in picture) plastic 3/4". Anchor locker drain.

Port side (not pictured - only one)

P1 - plastic 3/4". Bilge amidships, underneath cave.

Transom, port side (not pictured)

T1 - metal vent. Fuel tank vent.

[talman]

S1 - plastic 3/4". Bilge.

S2 - plastic 3/4". .Fish well.

S3 - plastic 1". Maceator.

S4 - plastic 3/4". Shower sump

S5 - metal. Head vent. the fuel vent is on the transom port side

S6 - plastic 3/4". Head sink drain

S7 - metal. Water tank fill vent

S8 - (not in picture) plastic 1 3/8" (not exactly sure of size). Galley sink drain

P1 - (not in picture) plastic 3/4". Bilge pump at the base of the cave..

The order might not be right.

I replaced the galley sink TH but do not remember it being hard. Now the TH in the closet, that is hard. I did not replace the scuppers, but would have had I kept the boat longer.

[Norton_Rider]

You may be better off replacing the holding tank vent vent with a straight thru hull made from plastic. The type used by Bayliner impedes the aeration necessary to maintain aerobic germs in the holding tank. The aerobic germs contribute to eliminating odors. Better yet, if possible, increase the tank vent size to 1" and replace the clear vent hose with sanitation hose. Plastic thru hulls are OK if made from Marelon.

[builderdude]

Tally's has them correct. Mine is a 93 model so a couple are different (don't have fish well drain) :

S-1 Engine bay bilge 1 1/8"

S-2 Flybridge floor drain 3/4

S-8 Gally sink 1 1/2"

S-9 Anchor locker drain 3/4"

All vent through hulls are 5/8" from the factory but as Norton Rider suggested, upsizing the holding tank vent and using a standard type through hull is a good idea.

[talman]

Here is my project link to do exactly what is mentioned above

http://www.baylinerownersclub.org/in...u-hulls#303228

[Solandri]

"talman" post=804117 wrote:
I replaced the galley sink TH but do not remember it being hard. Now the TH in the closet, that is hard. I did not replace the scuppers, but would have had I kept the boat longer.

Thanks. Very helpful. I can actually fit into the closet and reach the TH (with one arm) so don't anticipate that one being too difficult. I can contort my arm to touch the galley sink TH, but not enough to apply sealant, work a hose on, or tighten a hose clamp.

"Norton Rider" post=804122 wrote:
You may be better off replacing the holding tank vent vent with a straight thru hull made from plastic. The type used by Bayliner impedes the aeration necessary to maintain aerobic germs in the holding tank.

Isn't the point of using the vent-style TH to prevent seawater from splashing inside? I guess that's not a big a deal with the holding tank, other than making it fill faster.

Plastic thru hulls are OK if made from Marelon.

Yeah, I read numerous threads on Marelon vs metal. In the end I decided to go with metal because the Marelon THs would be the mushroom head style, sticking out about a quarter inch above the hull's surface. If I were to brush up against something with the side of the boat, it could crush and crack the TH head off, causing the rest of the TH to fall inside. I figure a metal TH would deform in that situation, but enough of it would stay intact to remain in the hole.

I plan to use Marelon for the anchor locker TH, since that one is easily accessible from inside the cabin. Worst case I can just shove a towel in the hole.

"builderdude" post=804123 wrote:
Tally's has them correct. Mine is a 93 model so a couple are different (don't have fish well drain) :

My fish well also doesn't have a drain. Either it came that way or a PO modified it so it can be lifted out and got rid of the drain. Guess I'll have to trace that hose to see where it goes.

[Norton_Rider]

I've had two boats with straight through thru-hulls for the holding tank vent. I've never had an issue with water getting in the tank.

My comment regarding plastic was specific to the holding tank vent. Plastic is better for this application because this thru-hull is in a very corrosive atmosphere.

[Iproff]

If your changing them to metal you need to connect them to the bonding system. The plastic ones are not or need to be connected to the bonding system.

Ken

[talman]

Ken, they are like a trim tab. They don't connect to any other metal, so there is no potential to make a battery. They really don't need to be bonded. Bennett even hedges on the need for a zinc. (I do have them)

As to the holding tank vent, you need a loop, but the location of the TH is WAY above the waterline. Even if it filled the holding tank, you'd only be taking on 15 or so gallons, if that much could get in.

The bigger TH for the holding tank completely eliminated any stank. Air and poo are a good combination. So to speak.

I talked to a fellow 2556 and he reminded me that we took the sink (or stove) out to do our TH's in the galley. It wasn't hard.

and SS is just plain sexier than plastic. :P

[builderdude]

No bonding on any of my stainless through hulls (all above the water line) no zinc on my tabs either, still look new. All that said, my boat sits on a trailer most of the time :lol:

[Iproff]

"talman" post=804218 wrote:
Ken, they are like a trim tab. They don't connect to any other metal, so there is no potential to make a battery. They really don't need to be bonded. Bennett even hedges on the need for a zinc. (I do have them)

As to the holding tank vent, you need a loop, but the location of the TH is WAY above the waterline. Even if it filled the holding tank, you'd only be taking on 15 or so gallons, if that much could get in.

The bigger TH for the holding tank completely eliminated any stank. Air and poo are a good combination. So to speak.

I talked to a fellow 2556 and he reminded me that we took the sink (or stove) out to do our TH's in the galley. It wasn't hard.

and SS is just plain sexier than plastic. :P

Every one of my metal thru hulls is connected to my bonding system by the manufacture (Sea Ray). Water conducts electricity and that can make them part of the system.

I agree not all need to be bonded but they bonded every one of mine and my trim tabs.

Ken

[Norton_Rider]

Here's a great article on bonding: https://www.google.com/url?sa=t&rct=...Vjju5Q&cad=rja

BTW, the one exception is a wooden boat. Zinc and bronze in contact with salt water form hydroxyl ions that eats into the wood. As a result, the latest thinking is not to bond thru hulls on wooden boats and use the minimum number of zincs necessary on prop shafts, rudders, etc.

[Solandri]

Which adhesive should I use? 3M 5200? 4200? or 4000? 3M recommends 5200 but I'm reading a lot of people saying it's overkill above water and too difficult to take off if I ever need to replace the thru-hull.

And I don't plan to bond these. The boat is trailered. If these thru-hulls are immersed in water long enough for corrosion to become a factor, I have much more serious problems to worry about than corrosion.

[Norton_Rider]

4200 should work fine.

[builderdude]

"Norton Rider" post=804505 wrote:
4200 should work fine.

Yup, I used 52 cause it's what I had layin around but 42 is "removable" :lol: