What's wrong with silicone?

[Chris611]

I am finishing up a repair and will be mounting my transom straps and ladder. I keep reading on here that everyone uses 3M 5200 adhesive sealant. What's wrong with using 100% 50year- silicone? I remember reading posts that talked about this a long time ago, but when I tried to search I can't seem to find them again. Is it the mold resistance, skrink? Not trying to start a fight, just trying to get educated and know why everyone's seems to be against silicone.

Thanks
Chris

 

[Bob_VT]

Re: What's wrong with silicone?

It does not "grip" properly to various materials. People have tried it and it does last the 50 years however it does not do the job you wanted it to do for anywhere near that time.

The marine 5200 is really tough stuff. I just have found that the advice we get here is "good advice" from a bunch of people who have been there.

On a recent project of mine (aluminum boat) someone used silicon and i was told to get rid of it. It was real easy to remove once I dug into it. I resealed the seams with Gluvit which was what everyone said to use. I doubt that will come out in my lifetime and never leak.

 

[fishingdan]

Re: What's wrong with silicone?

Chris,

Bob has it right. Exterior household silicone caulk just doesn't seem to adhere well for very long in a marine environment. Usually within a couple of days, you can just pull it off with minimal effort.

The 3M stuff is really good. Silkens also has a good product. You want something specific for marine use (above and below the waterline). Lately, I have used Marine Goop. It works really well too. The marine specific stuff in only a couple of more $ than the household stuff.

3M 5200 is intended for permanent installations. It isn't really permanent, but it is tenacious and not easily removed from previously cleaned surfaces.

3M 4200 is intended more for less permanent installations. For example, caulking a thru hull fitting that is being installed.

 

[Chris611]

Re: What's wrong with silicone?

Thanks guys. Thats what I was looking for. I have some Marine Goop that I found at the local farm store. I searched the old posts for Marine Goop and wasn't able to find anyone that said it was good or bad. I guess I will pick up some fast cure 3M 5200 just to be sure. It's for ladder mount bolts and transom strap lugs. Don't intend on needing to take them off.

Thanks
Chris

 

[studlymandingo]

Re: What's wrong with silicone?

If you read the specs on the 3M products, you will find the 4000 is rated for adhesion to both metal and porous surfaces, the 5200 and 4200 do not carry the same rating.

 

[epresutti]

Re: What's wrong with silicone?

Chris611,

Down here (Florida), people swear by the 5200, salt water tends to eat everything, I have a wood and fiberglass rebuild and I don't want water getting into any little nook or cranny. I use it on the end of every mounting screw and bolt I put in the boat.

Peace.

Ed.

 

[tashasdaddy]

Re: What's wrong with silicone?

there has been more rotten wood in the construction industry because of failing silicon seals, and caulk.

 

[fishingdan]

Re: What's wrong with silicone?

If you have the marine Goop, I would just use that. I used instead of 3m on one of my boats and it is holding up well. I bedded rail fittings with it and don't see any difference in performance between it and the 3m stuff.

 

[G DANE]

Re: What's wrong with silicone?

What's wrong with silicone? well I prefer the natural things any time !! Sorry, coundnt resist.

Silicone can be used, between i. exa. deck fittings and g/f, if nothing else is available. Apply liberally and tighten fitting extr after the silicone has set. The special stuff, like 5200 is harder, more adhesive and sticks to most surfaces.

 

[Chris611]

Re: What's wrong with silicone?

Well I ended up using 3M 5200. That stuff sure is expensive condering the tube says you have to use it within 24 hours. I guess I'm glad I did, so I don't have to worry about it leaking later. It was intersting to read all the replies. I figured 3M just slapped the word marine on it and tripled the price. Seems like anything marine is expensive because its a "luxury" sport. Anyway, thanks guys.

Chris

 

[Kevin70]

Re: What's wrong with silicone?

Don't get me started.

Water pump for my boat: $450.00
EXACT SAME PUMP for the car version of motor: $65.00