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Inspection port Sealing


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I am replacing the inspection ports on my boat after finding some were leaking. After taking a couple off, there was not really anything behind the outer flange for sealant. What are good options for sealant behind the new port? What is there telegraphed the port pattern, but is hard and probably does not seal properly any more. 

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Works even better if you do both the sealant flange and the cap....

Seriously, if the inspection port flange is plastic and only has four or five fasteners, I'd probably use 4200. If they're metal and/or have more fasteners, butyl could work well and would make it easier to disassemble in the future. 

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I would like to disassemble in the future. New one has 8 fasteners. I am guessing its 4200 on there now because id didn't stick to the port ring, but is the dull tan of the 3m sealants. 

I was thinking silicone or RTV but since it wont stick to either the hull or the port I would probably be reapplying. Butyl might be the ticket. 

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2 hours ago, gn4478 said:

Make a gasket with medium durometer Buna N and use Butyl tape on the screws.

 

If you're gonna use butyl tape at all, why mix materials? Butyl can handle the whole thing.

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29 minutes ago, Locus said:

Been leaning between butyl and 4200. Which would be easier to remove should I have to replace again? Probably butyl?

Butyl, by far.

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My impression is 5200 eats the plastic on most screw in deck plates. The plastic cracks everywhere . 
virtually all other sealants work fine if you prepare the surfaces properly and countersink the screw holes just a smidgeon. 

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Check the caulking label. Most polyurethanes are not good with plastics and say so. That includes Sika 241 and 5200. 4200 might be similar too. Also Polysulphide like LifeCaulk is supposed to be bad.

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I normally use Dowsil 795 (nee Corning 795), because it's inexpensive, easy to work with, and won't degrade the plastic port. Good adhesion, but easy to cut free with a box cutter when the time comes. 

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I've used 3M 4000UV on plastic deck plates and all sorts of other plastic without cracking problems. It is a polyether. It also doesn't yellow in the sun like 5200 or 4200. 

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On 1/18/2021 at 4:12 PM, Locus said:

I am replacing the inspection ports on my boat after finding some were leaking. After taking a couple off, there was not really anything behind the outer flange for sealant. What are good options for sealant behind the new port? What is there telegraphed the port pattern, but is hard and probably does not seal properly any more. 

On new builds , foam weatherstrip tape on the flange is used as a gasket  ,  with sika flex only used on the  bolts and holes 

for high load fittings a variety of gasket material are used... but the concept is the same ... sika to waterproof the bolts and holes 

the gasketed  hardware stays watertight and requires  very little cleanup when installed 

the substrate surface must be fair when using a gasket. 

if the surface is imperfect to the hardware ,  sika must be used to create a waterproof joint 

Esthetically Grey tape is best 

B50CCDFB-B2A8-4246-96D1-62139DD88CBD.jpeg

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Foam gasket won't work worth a $hit on a floppy plastic inspection cover flange. Unless you put a screw every cm. 

The best way to mount them is with 4000 in my opinion - and don't use any screws at all. 

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I have concerns about the foam tape as well. All of these will be underwater at some point so it needs to be pretty waterproof. I am going to try some tape on one and see how it goes. Certainly can remove and do the 4200 route. Seems like a good plan B. 

Screws now were only in the skin glass. I am filling those, over drilling and setting them in epoxy. That plus the sticky butyl or 4200 should hold them in. 

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Some will cringe but the best bedding compound I've used is still dolfinite. Removable and watertight for this application. They have white.  Of all the various goops we have used it lasts the longest by far before needing attention.

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6 minutes ago, SASSAFRASS said:

Some will cringe but the best bedding compound I've used is still dolfinite. Removable and watertight for this application. They have white.  Of all the various goops we have used it lasts the longest by far before needing attention.

Could work, but no one around here has any. Plus 60 bucks and I have to store 9/10 of a gallon. Don't need much for 5 5" ports. 

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1 hour ago, Locus said:

I have concerns about the foam tape as well. All of these will be underwater at some point so it needs to be pretty waterproof. I am going to try some tape on one and see how it goes. Certainly can remove and do the 4200 route. Seems like a good plan B. 

Screws now were only in the skin glass. I am filling those, over drilling and setting them in epoxy. That plus the sticky butyl or 4200 should hold them in. 

The foam tape seems to last forever 

the picture is a  lewmar  hatch that has been removed , exposing the  teak frame 

As you can see only foam tape was used to bed the hatch 2003DF13-4142-4B35-BBA7-0451133CAC74.thumb.png.b7a6c2d9fbd190daa4a3233658083f29.png, no compound 

the hatch was originally installed in 1994 

 

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But I assume that hatch only sees green water and spray, never truly under water. Mine will be under water 1-2 feet on capsize. Seems like the tape will absorb water and stay wet. 

 

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ok so after taking off all the ports I found that 2 look like they had 4200 behind them. Left a rubbery white residue that telegraphed the back of the port. But the port came off with little effort so might have been leaking. The other 2 were definitely 5200 but the paint peeled off the glass and I have a pretty clean surface there to work with.

Any tips on getting the 4200 off? Looks like 3M recommends  8984 for cleanup. Will it remove cured 4200? 

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This stuff works pretty well:

https://www.fisheriessupply.com/debond-corporation-marine-formula

I've had good luck with this stuff too, but it can be hard to find:

https://tbpconverting.com/product/dsr-5-bond-breaker/

Whatever you use, let it soften up the 4200 then get a sharp plastic scraper and use it to scrape away the bulk of the material. Re-apply, and scrape again. Each time, it'll soften up and break down more of the remaining material. After three or four rounds of this you'll get down to a "bare" (but likely contaminated) surface that's suitable for use with butyl tape.

If you want to use 4200 or some other goop, hit it with polishing compound first to expose a fresh, uncontaminated surface that'll adhere well. Do NOT clean with alcohol if you plan to use 4200 (or 5200) as it will inhibit adhesion. 

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1 hour ago, Locus said:

ok so after taking off all the ports I found that 2 look like they had 4200 behind them. Left a rubbery white residue that telegraphed the back of the port. But the port came off with little effort so might have been leaking. The other 2 were definitely 5200 but the paint peeled off the glass and I have a pretty clean surface there to work with.

Any tips on getting the 4200 off? Looks like 3M recommends  8984 for cleanup. Will it remove cured 4200? 

Sika , 3m In very soft

at the shipyard we use a medium stiff wire wheel ,on a right angle drill,  run at slow speed to mechanically  remove old compounds from flange surfaces  

 

solvents , due to health,  safety and environmental concerns are avoided 

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All the deck hardware on 'Secret Love' was originally laid down with Dolfinite. 1.5 years later, every single fitting leaked profusely. That shit had dried up & turned into dust.

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1 hour ago, Diamond Jim said:

What’s wrong with plain old bedding compound like Dolfinite?  It stays gummy and can be undone.

Cannot even find the stuff around here

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12 hours ago, Diamond Jim said:

What’s wrong with plain old bedding compound like Dolfinite?  It stays gummy and can be undone.

Dolphinite dries out rapidly 

dont use it for general exterior bedding on modern boats 

for some applications  butyl    Spaghetti strips can be used

butyl also has defects , viscosity and the effects of solvents ,  bleeding 

beware of carbon black butyl and aluminum 

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