Wayne,

Two votes for silicone, two for epoxy. Might it depend on the manufacturer? I have a Humminbird. If you can wait a second, I'll fetch my unerring instructions... Let's see, I think they're on this shelf...hmm..."Kama Sutra for Dummies"..."Autobiography of Red Skelton for Dummies" by Clem Cadiddlehopper..."DIY Nuclear Power for Dummies" by Homer Simpson...Ah, here it is, "Fishfinder Transducers for Dummies". Yup, says to use epoxy goo, and I don't know enough to risk angering the goo gods. I had the impression that you needed a dense, solid goo to shoot through, but seems to me if silicone goo gives accurate readings, what a great solution. Just my opinion. Installation info for Humminbird is at http://www.humminbird.com/hb_MoreSupport.asp?id=26

Correct me if I'm wrong on any of this, but I also think some confusion has been created by manufacturers in the use of the term "thru-hull", which used to mean you gotta drill a hole through the hull. With the newer transducers, thru-hull means it senses from inside the hull, through the hull, with no hullholes needed (I used to live in a hullhole. Be a good name for a waterfront bar). I think all of the popular fishfinders use the inside-the-hull transducers that can optionally be hung off the transom with a mounting bracket, but it'd probably be wise to make sure of what type of thru-hull they mean. Maybe someone can confirm if it's worth putting it as far forward on the hull as possible while still in an area that stays in contact with the water, since they are forward-looking and doing so would give a few more yards' notice of, to put it gently, an unexpectedly abrupt cessation of forward motion. On the other hand, these are short, shallow-draft boats; maybe it doesn't really matter.
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Sorry, I can't help it:
;)
Now that I think about it, the silicone idea sounded good at first, seein's how it works perfectly and all. But I gotta say, I think it shows a certain lack of commitment. I mean, how long could it take to reposition it? A couple of minutes? A nickel razor blade, a little scraping, a tiny scratch or two? Bah. Humbug (or Humminbird). That's not a REAL boat job. I think it's important to believe completely in one's own poor judgement, ignoring once again the lessons learned last time, and just slap 'er down in the wrong place to stay. It'll take me a good 5 or 6 hours and a couple hundred bucks to change its location if it doesn't read accurately, not to mention the cost associated with how I'll find out it doesn't read  accurately. Apparently, THAT'S what boat ownership's all about. As a newbie, I've learned BOAT stands for "Break Out Another Thousand".

Fortunately, mine works great.
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;)
This Month's Useless M-Fact:

If you are lucky enough not to have seen the steel shot used for ballast in the 15s and 17s (at least that's what the boatyard said it was), there is a picture of some of the little buggers on the MSOG site at http://msog.org/how-to/how-to_flotjet.cfm  (second ditty). I had no idea of their size, but seeing them naturally aroused my need to know: How many more of these will I be seeing someday, and how can I put them to good use? I mean they're just slowing down the boat where they are now.

So I took some to work Friday to be weighed on a balance in one of the labs where a fellow (actually fella) sailor works and we found that the weight of 10 of them averaged .104 grams each (it was a slow day for both of us). Using a nice round number of 454.00889 grams per pound and ignoring significant figures, there are 4365.47 of them to a pound, which means an M-15 keel of 275 pounds contains 1,200,504, and an M-17's keel of 580 pounds has about 2,531,972 of the little guys snuggled up in there. I read that lead is used in the M-23, and I found no mention if it's in the form of shot or not. Feel free to check my arithmetic, I ran out of fingers and toes pretty early in the count, after 24. 

Now Bob Eeg and all M-owners can brag that each boat contains well over a million, or two and a half million, separate components fitted together perfectly, even though most of mine are probably slowly rust-welding themselves together.

Plus, I've figured out a way to do get rid of them AND not have to learn how to do reverse-routing on the GPS. I'm gonna drill a small hole in the keel and let them dribble out one at a time. Then I'll epoxy an 11" diameter DetectorPro Headhunter Pulse underwater metal detector with self-draining anodized aluminum rod of durable baked-on powder coating and permanently encapsulated high-output piezoelectric headphone transducers ($699 at http://www.detectorpro.com/headhunterpulse.htm) to my hull and just squeal my way back.

I gotta lay off Car Talk.

Doug the Circus Freak



At 11:21 PM 4/26/02 -0700, you wrote:
Wayne,
 
    I mounted a through-hull transducer in my M15 on the inside of the hull just forward of the keel/centerboard.  I used clear silicone instead of the epoxy supplied with the transducer, just in case I needed to move the unit to a different position later.  Use a big glob of silicone and make sure there are no bubbles it.  Gently weight the transducer until the silicone sets.  My Eagle Magna depth sounder/fish finder works great with this installation... and I didn't have to drill another hole in the boat.
 
    Joe Kidd  M15 #207  "Poco a Poco"
----- Original Message -----
From: wayne yeargain
To: montgomery_boats@mailman.xmission.com
Sent: Friday, April 26, 2002 8:48 PM
Subject: Re: M_Boats: transducer position

Doug, do I read your message right that you mount your depth transducer on a bed of caulking to the hull?
I thought they had to be immersed in water or some other liquid, sealed inside a short section of pvc
pipe,or other such container.
Do they work simply sealed to the inside  of the boat ?
 
Wayne M17 #204 Intrepid