Why not silicone?

Hi Kids,

I am about to mount the transducer on my new Matrix fishfinder and I am curious to know why people prefer marine goop over silicone.  It seems as though some people have trouble with the marine goop, especially in warm/hot weather.  The marine goop states that it is stable to 150 degrees, while the silicone states that it is stable to 400 degrees.  I live in a super hot area where summer temperatures over 100 fairly common in the summer.  This I am sure is compounded by upside down kayak storage and a kayak sitting on top of a car in the hot sun.  I really do not want to deal with the transducer falling off.  Is there some reason why silicone is not preferred?

Thanks, Sean

it is possible that the sonar impulse would not shoot through silicone. i know that it will shoot through the 3m products.

The softer the material, the worse it is for transmitting sonar signals.

Ideally you would use super hard epoxy to mount the transducer (well, ideally it would not be shoot through hull in the first place if you are interested in max sensitivity), but with the hull flex, it would pop off.  Marine goop is pretty soft but seems to work for many people.

Personally, I hang my transducer over the side of my yak with a mounting bracket that hangs on my Rhyno Bar.

MolBasser

I used marine epoxy twice, and it popped off in short order.  Then I switched to aquarium sealant (silicone) that was laying around and it hasn't been a problem since.  The only time I had trouble getting a reading was off moss landing where I couldn't see the bottom past 300' or so.  Not sure if it was the silicone or the shoot-through that degraded it but it's supposed to do 600'.  Since I used epoxy first, the bottom of the transducer was perfectly fit to the hull, so the layer of silicone is probably extremely thin.

I think the silicone flexes a bit when the boat is bumped rather than pop off, anyway it's been over a year, wheras the epoxy only lasted a couple weeks.