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Author Topic:   application of silicone sealant

gmoulder posted 09-01-2011 11:59 AM ET (US)
What is the best way to apply / use silicone sealer? I have read that you should apply the stuff to both mating surfaces and immediately put them into contact. I have also read that you should apply the sealant to one of the two surfaces, let it firm up and then put the other surface into contact; this way you do not "squish" the sealant away from the joint and minimize the sealing material. This weekend, I plan to finish the engine lowering business and replacing the transom thru-hill drains, and it would be good to know the right way to use the sealant. Thanks. Glen
dscew posted 09-01-2011 12:59 PM ET (US)
I would make sure the product you're using is designed and specified for your application and follow the manufacturer's recommendations. Anything below the waterline is especially problematic. Generally, silicone isn't good for marine use, although I guess some of them are rated for that. Be careful.
contender posted 09-01-2011 01:14 PM ET (US)
Anything below the water line you need to use 5200 by 3M for a sealer, if you plan to use the boat in a day (24hrs) you need to get the fast cure 5200....The humidity and heat factor will change the curing times need to read the instructions on the tube...
Sourpuss1 posted 09-01-2011 01:14 PM ET (US)
I have used silicone based products to bed deck fixtures, with varying degrees of success.
Use 5200 on the thru-hull fittings. It is permenent, and very good for anything below the water line.
Do a search on brass thru hull replacement for detailed instructions!
Tohsgib posted 09-01-2011 01:45 PM ET (US)
Not sure I would use 5200 unless you NEVER want to remove it again. Silicone type sealant or maybe even 4200 I think is fine. The same stuff you use to bed your engine bolts and brass drain tubes should be plenty for a through hull.
captainbrent posted 09-01-2011 05:31 PM ET (US)
I would recommend using 3M 5200 for anything that is below the waterline. That is what marine shops that install engines use on the mounting bolts and I have had great success with it on both of my whalers. By the way, I had to remove the mounting bolts on my 13 (installed with 5200) after several years and with a bit of finesse, they came out. A very small piece of gelcoat came along, but it wasn’t a problem. As previously indicated, play close attention to the cure time. In Florida, regular 5200 takes almost a week to fully cure. I have used it to “bed” brass drain tubes, at it works great. Above deck, BW actually used silicone to seal seams and it works fine. That is what fish tanks are sealed with. The key is to have both surfaces dry and clean.

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Author	Topic: application of silicone sealant
gmoulder	posted 09-01-2011 11:59 AM ET (US) What is the best way to apply / use silicone sealer? I have read that you should apply the stuff to both mating surfaces and immediately put them into contact. I have also read that you should apply the sealant to one of the two surfaces, let it firm up and then put the other surface into contact; this way you do not "squish" the sealant away from the joint and minimize the sealing material. This weekend, I plan to finish the engine lowering business and replacing the transom thru-hill drains, and it would be good to know the right way to use the sealant. Thanks. Glen
dscew	posted 09-01-2011 12:59 PM ET (US) I would make sure the product you're using is designed and specified for your application and follow the manufacturer's recommendations. Anything below the waterline is especially problematic. Generally, silicone isn't good for marine use, although I guess some of them are rated for that. Be careful.
contender	posted 09-01-2011 01:14 PM ET (US) Anything below the water line you need to use 5200 by 3M for a sealer, if you plan to use the boat in a day (24hrs) you need to get the fast cure 5200....The humidity and heat factor will change the curing times need to read the instructions on the tube...
Sourpuss1	posted 09-01-2011 01:14 PM ET (US) I have used silicone based products to bed deck fixtures, with varying degrees of success. Use 5200 on the thru-hull fittings. It is permenent, and very good for anything below the water line. Do a search on brass thru hull replacement for detailed instructions!
Tohsgib	posted 09-01-2011 01:45 PM ET (US) Not sure I would use 5200 unless you NEVER want to remove it again. Silicone type sealant or maybe even 4200 I think is fine. The same stuff you use to bed your engine bolts and brass drain tubes should be plenty for a through hull.
captainbrent	posted 09-01-2011 05:31 PM ET (US) I would recommend using 3M 5200 for anything that is below the waterline. That is what marine shops that install engines use on the mounting bolts and I have had great success with it on both of my whalers. By the way, I had to remove the mounting bolts on my 13 (installed with 5200) after several years and with a bit of finesse, they came out. A very small piece of gelcoat came along, but it wasn’t a problem. As previously indicated, play close attention to the cure time. In Florida, regular 5200 takes almost a week to fully cure. I have used it to “bed” brass drain tubes, at it works great. Above deck, BW actually used silicone to seal seams and it works fine. That is what fish tanks are sealed with. The key is to have both surfaces dry and clean.