Shoot through hull transducer

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Oct 6, 2007
Vessel Name
Vessel Make
2003 Monk 36
I would like to mention that I installed a shoot through the hull transducer today. I tried locating a good spot which would give me an accurate reading, first I used a ziplock bag filled with water against the hull, and*pressed the transducer down*on it (I had read somewhere this would work to locate*a spot) but I got wildly fluctuating numbers. I had also read about using a glob of toilet wax ring wax to hold the transducer in place instead of epoxy etc. so I got*a*wax ring, it*was too cold at first so I stuck it in the microwave on defrost for about 3- 4 miutes and it became pliable. I made a golfball or a bit bigger sized ball* placed it in a likely* looking spot and presed the transducer down on it holding the transducer bottom parallel with the water level. It immediately began marking a number which is correct for the slip and stayed steady.* So, I feel this will be a good solution to that problem. My transducer is located in an out of the way, well protected area so doubtfull it will be knocked off of the wax. It remains to be seen how the wax will hold up in our hot weather and hotter engine rooms. I had read the water will keep the hull cool enough to stop the wax from softening, but, the water around here gets pretty hot in summer so we'll see about that.
The depth finder is a Humminbird 610 digital readout*which will serve as a standby unit.
Steve W

-- Edited by Steve on Wednesday 16th of December 2009 07:38:54 PM
I have a "shoot through" transducer as well. I am using a standard Garmin through hull plastic transducer for my 3210 comob chart plotter. I cut a 4" piece of PVC pipe at the same angle as the hull. Then applied some 3M4000 goop to the angled end and wedged it in place to cure. I cut a hole in a 4" PVC pipe cap and mounted the transducer through this. Filled the pipe with water (I have heard mineral oil works good for this as well and won't evaporate) mounted the cap with the transducer immersed in the water and it works great. No additional hole in the hull and no junk gettting caught on anything protruding through the hull. The only drawback is that the water temp is not accurate. The water temp hardly changes around here anyway so no big dea.
Mine is a Humminbird transom mount depth/temp ducer that I mounted to the inside of a 4" ABS pipe cut so the ducer is level and epoxied to the hull in an out of the way place. SEA 10 oil (leftover from topping up the steering hydraulics) and I get a good reading. Temp varies only slightly from cool ER to after hours of running. Using the transom mount that comes free with the sounder is way better than $300 for the thru hull ducer, then making up the angled blocks and hauling out to install it. I keep epoxy on hand and the oil was surplus, so my only expense was $5 for the short length of black pipe and cap.

I also have a Garmin unit that I was able to buy with an inside mount transducer. All the same principals but slightly more attractive design. That unit doesn't come with temp, as Garmin won't let you get the inaccuracy of influence from the heat of the ER. The display can handle temp, but for their units you have to buy the outside mount transducer to take advantage of it. I solved that problem with the Humminbird.

Now all those dead transducers hanging under my hull will eventuall have to be removed and the holes patched. Seems you can never use the old transducer on the newer display heads.

I knew my hull was solid layup and I had inside mount ducers in other boats, so I didn't bother with the bag of water, just went ahead and mounted, with good results.
I'm hoping to upgrade to a fish finder-style unit from my sounder-only unit. I want to see a graphic of the bottom and not just a number. Can I see a few pics of these installs? I'm trying to keep it on-the-cheap (less than $150... gift card for xmas
), so I hope to use the included transducer rather than buy another in-hull unit.

Gonzo, Humminbird has lots of inexpensive models to chose from theyare at most sport or marine stores.
I have heard of people using the standard transducer as an inhull unit, Koliver mentions that in his post. I will take a picture of mine and post it to you next week.
Steve W
Can you recommend one that's better for the trawlers than another? And where is the "best" place to mount the transducer? There are several down there now and I am kind of running out of space. I would like to have it closer to the bow, but the only place up there (under the v-berth) may have to shoot thru the keel or off to one side. Can it? Can you adjust the angle that it sits inside these 4" tubes?

(that's why a pic might help... looking forward to seeing them)
On a previous boat I mounted the transducer under the Vee berth, where the hull rose at 45 deg, so the tube was cut to the angle, the transducer sat in water and I got a good reading.
On this boat, the bow is too far away, cable runs would be awkward, and there was a section of hull not being used, under the autopilot pump, so in it went. There the hull rises at about 20 degrees, it is well away from the keel, so the mount was easy. Cut the pipe to the deadrise angle and epoxy it in. simple. With a transom mount transducer, drill the holes in the pipe to mount the transducer in the pipe before gluing the pipe in place.
Bob's yer uncle.

So is filling it with oil better than water? Does either give a temp reading more-or-less closer to the actual average water temp? Assuming it's close to the ER temp before getting underway, that is.

(Although, honestly, I don't see much of the need for temp readings except that it would just be something interesting to know. Even IF it was accurate with a thru-hull sensor. But I don't fish... yet.)
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