Spacer for Transducer?

Mar 15, 2020
10
Catalina 27 Galesville
Hey all - I'm working up the courage to install my new Airmar B619 through hull transducer, and trying to find every reason to put it off (half joking). My question is why I see people using a piece of wood as a spacer when installing through hulls? The Airmar came with a plastic/rubber (something) spacer, so I'm guessing that's sufficient? Seeing as the hull is a bit curved, I'd think that the spacer (which is flat) would keep it from keeping consistent pressure over time. I've attached a photo of where were thinking.
IMG_20200606_164033.jpg
 
Jan 4, 2006
3,912
Hunter 310 West Vancouver, B.C.
That is something I just don't understand. One hears of spacers, oil baths, voodoo enhancers, and every other sort of crap imaginable for installing thru hull sonar sounders. The theory is that they and the hull need intimate contact with an acoustic permeable material in order to work well. One (and only one) of the more successful materials is a half inch thick bubble-free puddle of silicone sealer. Toilet bowl wax ring sealer seem to be another which I have not had the opportunity to use. Might tend to move over the years in hot weather.

Take a look here (see #6) to see the preliminary steps before mounting it anywhere:


For the water bag test, fill the plastic bag under water in the sink to make sure it's bubble free.
 
Jan 4, 2006
3,912
Hunter 310 West Vancouver, B.C.
@SVCeviche , I must apologize as I just re-read you post and realize you are contemplating a THRU HULL and not an IN HULL transducer.

DON'T EVEN THINK OF DOING IT. IT IS NOT NECESSARY ! ! ! !

Modern transducers (and maybe even older ones) are perfectly capable of shooting through solid fiberglass hulls with identical results to a thru hull. This is why you test the hull composition first. I suspect even a spot of delamination will disqualify a pre-selected spot. The in hull I installed was in a friend's 42 ft. Cat and we get the same readings with my factory installed thru hull transducer when we are out and alongside one another.
 
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Mar 15, 2020
10
Catalina 27 Galesville
Ralph, I appreciate the comment. I'm not kidding when I say that we finished the installation right as I got your response. Curious about why you're against the thru hull, though? Is it just the additional benefit vs risk?
 
Jan 4, 2006
3,912
Hunter 310 West Vancouver, B.C.
Just got this thing about holes in the hull. Particularly when they're below the water line :yikes:.
 

Ward H

.
Nov 7, 2011
3,129
Catalina 30 Mk II Barnegat, NJ
Depth transducers are powered by the depth instruments. Not all transducers can be mounted and work properly in the hull if the instrument is designed for a thru hull mounted transducer. At least according to Raymarine.

PS: I believe the answer to your original question is that depth transducers are larger than most water intake/drain thru hulls. The smaller sized thru hulls need a spacer of a larger diameter to spread the load of opening and closing the thru hull valve.
 
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