# GE Silicone I vs. Silicone II?



## SEMIJim (Jun 9, 2007)

The instructions for the in-hull transducer for my GPS/chartplotter/sonar recommend using either GE Silicone I or Silicone II for fastening the transducer's "bathtup" to the inside of the hull. I'm wondering if there's much difference between these two sealants and if anybody has a recommendation of one over the other, and why?

TIA,
Jim


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## sailingdog (Mar 19, 2006)

SEMIJim-

One quick question—Does your boat have a cored hull? If it does, the transducer has to be over an area that is not cored.. it won't work through a cored hull.


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## SEMIJim (Jun 9, 2007)

sailingdog said:


> SEMIJim-
> 
> One quick question-Does your boat have a cored hull?


Nope. Read up on the boat's construction and asked on the p30 mailing list about in-hull transducers before buying the GPS .

Thanks for the warning, tho.

Jim


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## sailingdog (Mar 19, 2006)

i don't think that there's a huge difference between the two.


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## bobmcgov (Jul 19, 2007)

Jim: Plump for the Silicone II if you can get it. It has better adhesion to plastics and fiberglass, is mildew-resistant, has lower shrinkage, and doesn't stink like an overturned vinegar cruet. Iz good schtuff. (At $6 a tube, it bloody well ought to be!) Keep lots of rags and some paint thinner handy for cleanup. Water alone won't remove mess. There's usually mess. (The GE caulks DO come with their own snap-on cap, however. If you can keep it on.)


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## sailingdog (Mar 19, 2006)

Bob's got a good point. The acetic acid curing silicones really don't have any use on a boat—especially not as a sealant, since they can promote corrosion.


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## SEMIJim (Jun 9, 2007)

Thanks for the info, Bob. That's just what I was looking for. GE Silicone II it is 

Jim


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## Maine Sail (Jan 6, 2003)

*Semi!*

make sure you test the spot before adhering anything to the inside of the hull. My preference is a zip lock baggy filled with water. Simply place the transducer on the baggy then set the baggy where you want the transducer to go. If there is any air in the laminate, which is very common on hand laid hulls, the transducer will have poor performance.

I HATE silicone for one reason and that reason is that NOTHING removes it except for sand paper and grinding away your hull. Even when wet, and not cured, nothing totally removes it for clean up not mineral spirits not acetone not MEK.. If it were me I'd be using Sikaflex or 3M4200. Silicone is NOT allowed on my boat!

One other option is a toilet bowl wax ring $1.99 at most hardware stores. It molds nicely to the hull and you can just plop the transducer into it and head off sailing. A buddy of mine is going on his fifth season with his "temporary" and "test fit" for his ducer with a wax ring..


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## SEMIJim (Jun 9, 2007)

halekai36 said:


> make sure you test the spot before adhering anything to the inside of the hull.


Of course.



halekai36 said:


> My preference is a zip lock baggy filled with water. Simply place the transducer on the baggy then set the baggy where you want the transducer to go. If there is any air in the laminate, which is very common on hand laid hulls, the transducer will have poor performance.


Very well, I'll consider the zip-lock baggy method. (I was going to use the K-Y method. Seemed simpler.)



halekai36 said:


> If it were me I'd be using Sikaflex or 3M4200. Silicone is NOT allowed on my boat!


Instructions *specifically and explicitly* say not to use 4200. (Tho I _suspect_ the reason may be because of end-users getting the surface prep wrong and ending-up with mineral oil or whatever leaking all over the place and a non-functional sonar.) What is "Sikaflex?"



halekai36 said:


> One other option is a toilet bowl wax ring $1.99 at most hardware stores. It molds nicely to the hull and you can just plop the transducer into it and head off sailing. A buddy of mine is going on his fifth season with his "temporary" and "test fit" for his ducer with a wax ring..


Thanks for the idea, but I think I'll just stick with the installation instructions .

Jim


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## sailingdog (Mar 19, 2006)

FYI- Polyureathane-based sealants can attack plastics, and that is probably why 4200 is contra-indicated.


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## SEMIJim (Jun 9, 2007)

sailingdog said:


> FYI- Polyureathane-based sealants can attack plastics, and that is probably why 4200 is contra-indicated.


That would make sense, being as the plastic "bathtup" the transducer locks into is... uh... plastic . Thanks for clearing that up.

Jim


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## 42ndstreet (Oct 15, 2004)

Jim, what are you using for displays in the cockpit? I am trying to pry my wallet open to do the same project.


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## SEMIJim (Jun 9, 2007)

I'm using a Garmin 498. It's mounted on a home-brew swivel-arm that's attached to the inside cabin bulkhead on the port side of the companionway. When I want to look at the GPS from inside the cabin, I swivel it in. When we want to see it from the cockpit, it swivels out so it's sitting in the upper left of the companionway as you're looking forward.

That home-brew swivel-arm the PO made is a bit light for my GPS, which is larger and heavier than the PO's was, so I'll probably eventually replace it with one of the (more substantial) commercial products I've seen mentioned here on Sailnet before. Something that would allow us to move it actually _outside_ the companionway entrance would be good, because, as it is, it's kind of tricky getting past it.

Btw: The Garmin 498, being last year's model, is on clearance many places. It's hard to beat for the price you can get it for right now. Comes pre-loaded with U.S. coastal and Great Lakes cartography. If you don't want the sonar, you can save a few bucks going with the 492.

Jim


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## Freesail99 (Feb 13, 2006)

I mounted my 498c on my edison pedistal using a piece of teak and some U bolts.


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