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Author Topic:   Sealant

Anthony posted 11-18-2003 11:39 AM ET (US)
What type of sealant should be used for bolts, screws, ect.. that go into the hull? Also, what is used to fill holes from an aux engine mount, swim platforms, ect?
ShrimpBurrito posted 11-18-2003 07:08 PM ET (US)
I'd use a silicone sealant for screws that go into the hull.
For proper methods of filling holes, you'll find more than you ever wanted to know through the search engine. Just click "Search" in the upper right hand corner on most screens of the Forum.
Steve Leone posted 11-19-2003 12:44 AM ET (US)
Use Sikaflex. Use wood dowels and Marinetex to fill holes and finish with a Spectrum gelcoat kit if you want to get fancy.
kingfish posted 11-19-2003 11:35 AM ET (US)
Anthony (and ShrimpB)-
Silicone won't hold up as a sealant over the long haul.
Sikaflex, as per Steve Leone, 3M 4200, BoatLife...look for polyurethanes or polysulfides...
Anthony posted 11-19-2003 12:15 PM ET (US)
OK, Thanks for the information.
Anthony
ShrimpBurrito posted 11-19-2003 12:18 PM ET (US)
Thanks for the info as well. Gotta add that to my boat encyclopedia.
whalerajm posted 11-19-2003 03:58 PM ET (US)
Guys...
Please take this advise one step further for me...
When using the likes of a 3M 4200, when and how do you apply? I'm assuming you're using the Marinetex to hold wood dowel in place...when cured you resink screw into dowl...when how do ypou use the 3M 4200?
If screw hole is not stripped out and all you want to do is seal it do you fill hole and deck surface with 4200 and sink screw before it's cures?...or do you wait until it cures, redrill and sink screw?
Sorry for the simplicity of the info I require here...I have to admit I've been using silicon as a sealant and probably have a lot of old work to re-do...
kingfish posted 11-19-2003 05:32 PM ET (US)
If you have access to the surface of the fiberglass, countersink the screw hole *just a little* if it is not already, and use that as a "well" to apply a small squeeze of the sealant before you drive the screw through it; drill the hole first, if not already done.
If you don't have access to the fiberglass surface (re-anchoring a bracket or something that is not going to be removed), squeeze a small amount of the sealant into the hole the screw is going to be driven through then drive the screw..
whalerajm posted 11-20-2003 10:09 AM ET (US)
When using polyeirothane/polysulfides as a sealant b (vs silicone) for screw holes into deck or hull, how difficult is it to remove these screws down the road? Can they be backed out or do you have to drill them out?
Tom W Clark posted 11-20-2003 10:26 AM ET (US)
whalerajm,
It will not be difficult to remove them at all.
It is a myth that if you use a caulk like 3M 4200 or even 5200 (which is a more powerful adhesive) you won't be able to get the screw out later. It IS true that if you bed something with significant surface area to your boat, it will be very hard to remove and may in fact pull some gel coat off with it. This is true of some silicones as well (been there, done that).
Actually, I think silicone is suitable for some holes like engine mounting bolt holes, but for small screws, especially those below the waterline I prefer polyurethanes like those mentioned above.
For those of you shopping for caulk:
3M 101 is a polysulfide
3M 5200 and 5200 Fast Cure are very tenacious adhesive caulks
3M 4200 and 4200 Fast Cure are still pretty good adhesives, but are designed to give you a better chance of removing the caulked part (like a transom mounted transducer) but it still sticks very well.
Sika 241 and 240 (the slow curing version of 241) are like 5200. Very strong adhesive.
Sika 231 is less grippy and intended for bedding.
Sika 1A is a very strong adhesive and is sold not in boat stores but in construction supply houses. Significantly less expensive and not different in any appreciable way than 241.
ShrimpBurrito posted 11-20-2003 12:49 PM ET (US)
Tom - why do you say that silicone would be ok for motor mounts (like what I did just a few days ago), but not smaller screws?
Tom W Clark posted 11-20-2003 12:54 PM ET (US)
Dave,
I do think silicone would be OK for smaller screw holes, the polyurethanes are just a little more tenacious and do not end up interfering with any gel coat patch work that may occur in the future.
Montauk posted 11-21-2003 11:52 AM ET (US)
I would have to disagree on using silicone for engine mounting bolts although I have used it in the past. Some OMC Manuals state that a polysulfide caulk should be used, and the reason is silicone is degraded by gas and oil. I would shy away from using 5200 on this application for two reasons: first, if the surface is properly prepared and the 5200 correctly applied the washers and bolt will need to be heated when removing, and could remove gelcoat in the process. Second, you are fastening the motor to the boat mechanically and there is no need for a chemical bond. Use polysulfide and spend the money saved on gas to use the boat!
triblet posted 11-22-2003 10:01 AM ET (US)
Another adavantage of polysulfide (101) is that water cures it
and you can splash the boat more or less immediately.
Normal 5200 takes a week.
And it will keep in the tube for months, 5200 for days (more
if you bag it and put it in the freezer, but then 101 would
keep for years that way).
A downside is that 3M appears to only make 101 in full
caulk gun tubes now, no small squeeze tubes anymore.

Chuck
Tom W Clark posted 11-22-2003 11:41 AM ET (US)
I have heard that gas and oil will affect silicone, but that has never been my experience with it. Of course, there are LOTS of different silicones, some much tougher than others.
Chuck is correct that polysulfide will cure by moisture, but this is true of polyurethane as well. Silicone must be allowed to dry before it gets wet.
3M 5200 will cure slowly but 5200 Fast Cure will cure overnight. 3M 101 cures very slowly too. Brian Blazer Jr. (Outrageman) caulked the seem around the fuel tank cover on his old Outrage with a polysulfide and there was a thread where he described the process.
In the end it came out well but I seem to remember it took over a week for the polysulfide to cure.
I don't think there is anybody who would recommend using 3M 5200 for mounting an outboard motor. Anybody who does is in for a very difficult and ugly job of removing the mounting bolts and caulk later.
kingfish posted 11-22-2003 05:03 PM ET (US)
I don't hardly use 5200 for anything due to the permanent nature of the bond it develops, and my propensity to change my mind. I do use 4200 (fast cure) almost exclusively for any kind of sealant or adhesive around my Whalers, short of areas I use epoxy for. I just finished the process of removing a 90 HP Johnson from a Montauk that had been mounted with 4200 about two years ago, and it was doable.

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Author	Topic: Sealant
Anthony	posted 11-18-2003 11:39 AM ET (US) What type of sealant should be used for bolts, screws, ect.. that go into the hull? Also, what is used to fill holes from an aux engine mount, swim platforms, ect?
ShrimpBurrito	posted 11-18-2003 07:08 PM ET (US) I'd use a silicone sealant for screws that go into the hull. For proper methods of filling holes, you'll find more than you ever wanted to know through the search engine. Just click "Search" in the upper right hand corner on most screens of the Forum.
Steve Leone	posted 11-19-2003 12:44 AM ET (US) Use Sikaflex. Use wood dowels and Marinetex to fill holes and finish with a Spectrum gelcoat kit if you want to get fancy.
kingfish	posted 11-19-2003 11:35 AM ET (US) Anthony (and ShrimpB)- Silicone won't hold up as a sealant over the long haul. Sikaflex, as per Steve Leone, 3M 4200, BoatLife...look for polyurethanes or polysulfides...
Anthony	posted 11-19-2003 12:15 PM ET (US) OK, Thanks for the information. Anthony
ShrimpBurrito	posted 11-19-2003 12:18 PM ET (US) Thanks for the info as well. Gotta add that to my boat encyclopedia.
whalerajm	posted 11-19-2003 03:58 PM ET (US) Guys... Please take this advise one step further for me... When using the likes of a 3M 4200, when and how do you apply? I'm assuming you're using the Marinetex to hold wood dowel in place...when cured you resink screw into dowl...when how do ypou use the 3M 4200? If screw hole is not stripped out and all you want to do is seal it do you fill hole and deck surface with 4200 and sink screw before it's cures?...or do you wait until it cures, redrill and sink screw? Sorry for the simplicity of the info I require here...I have to admit I've been using silicon as a sealant and probably have a lot of old work to re-do...
kingfish	posted 11-19-2003 05:32 PM ET (US) If you have access to the surface of the fiberglass, countersink the screw hole just a little if it is not already, and use that as a "well" to apply a small squeeze of the sealant before you drive the screw through it; drill the hole first, if not already done. If you don't have access to the fiberglass surface (re-anchoring a bracket or something that is not going to be removed), squeeze a small amount of the sealant into the hole the screw is going to be driven through then drive the screw..
whalerajm	posted 11-20-2003 10:09 AM ET (US) When using polyeirothane/polysulfides as a sealant b (vs silicone) for screw holes into deck or hull, how difficult is it to remove these screws down the road? Can they be backed out or do you have to drill them out?
Tom W Clark	posted 11-20-2003 10:26 AM ET (US) whalerajm, It will not be difficult to remove them at all. It is a myth that if you use a caulk like 3M 4200 or even 5200 (which is a more powerful adhesive) you won't be able to get the screw out later. It IS true that if you bed something with significant surface area to your boat, it will be very hard to remove and may in fact pull some gel coat off with it. This is true of some silicones as well (been there, done that). Actually, I think silicone is suitable for some holes like engine mounting bolt holes, but for small screws, especially those below the waterline I prefer polyurethanes like those mentioned above. For those of you shopping for caulk: 3M 101 is a polysulfide 3M 5200 and 5200 Fast Cure are very tenacious adhesive caulks 3M 4200 and 4200 Fast Cure are still pretty good adhesives, but are designed to give you a better chance of removing the caulked part (like a transom mounted transducer) but it still sticks very well. Sika 241 and 240 (the slow curing version of 241) are like 5200. Very strong adhesive. Sika 231 is less grippy and intended for bedding. Sika 1A is a very strong adhesive and is sold not in boat stores but in construction supply houses. Significantly less expensive and not different in any appreciable way than 241.
ShrimpBurrito	posted 11-20-2003 12:49 PM ET (US) Tom - why do you say that silicone would be ok for motor mounts (like what I did just a few days ago), but not smaller screws?
Tom W Clark	posted 11-20-2003 12:54 PM ET (US) Dave, I do think silicone would be OK for smaller screw holes, the polyurethanes are just a little more tenacious and do not end up interfering with any gel coat patch work that may occur in the future.
Montauk	posted 11-21-2003 11:52 AM ET (US) I would have to disagree on using silicone for engine mounting bolts although I have used it in the past. Some OMC Manuals state that a polysulfide caulk should be used, and the reason is silicone is degraded by gas and oil. I would shy away from using 5200 on this application for two reasons: first, if the surface is properly prepared and the 5200 correctly applied the washers and bolt will need to be heated when removing, and could remove gelcoat in the process. Second, you are fastening the motor to the boat mechanically and there is no need for a chemical bond. Use polysulfide and spend the money saved on gas to use the boat!
triblet	posted 11-22-2003 10:01 AM ET (US) Another adavantage of polysulfide (101) is that water cures it and you can splash the boat more or less immediately. Normal 5200 takes a week. And it will keep in the tube for months, 5200 for days (more if you bag it and put it in the freezer, but then 101 would keep for years that way). A downside is that 3M appears to only make 101 in full caulk gun tubes now, no small squeeze tubes anymore. Chuck
Tom W Clark	posted 11-22-2003 11:41 AM ET (US) I have heard that gas and oil will affect silicone, but that has never been my experience with it. Of course, there are LOTS of different silicones, some much tougher than others. Chuck is correct that polysulfide will cure by moisture, but this is true of polyurethane as well. Silicone must be allowed to dry before it gets wet. 3M 5200 will cure slowly but 5200 Fast Cure will cure overnight. 3M 101 cures very slowly too. Brian Blazer Jr. (Outrageman) caulked the seem around the fuel tank cover on his old Outrage with a polysulfide and there was a thread where he described the process. In the end it came out well but I seem to remember it took over a week for the polysulfide to cure. I don't think there is anybody who would recommend using 3M 5200 for mounting an outboard motor. Anybody who does is in for a very difficult and ugly job of removing the mounting bolts and caulk later.
kingfish	posted 11-22-2003 05:03 PM ET (US) I don't hardly use 5200 for anything due to the permanent nature of the bond it develops, and my propensity to change my mind. I do use 4200 (fast cure) almost exclusively for any kind of sealant or adhesive around my Whalers, short of areas I use epoxy for. I just finished the process of removing a 90 HP Johnson from a Montauk that had been mounted with 4200 about two years ago, and it was doable.