Thru hull Triducer installed in Ballast tank, hole in boat!

[Wes T]

Tell me if this is a crazy Idea, but I'm considering installing a thru-hull (drill a hole) transducer inside the ballast tank of my M. I'd be using a Raymarine bronze unit with farling block that measures depth, speed, and temp.
I want the sensor to be in-front of the dagger board. I thought that I could cut a 6 inch hole in the top of the ballast tank (under the V-berth, maybe a little more aft) and then drill through the bottom of the boat to mount the triducer. I would use a screw on deck plate to seal the hole on the top of the ballast tank that I cut for access, this should make it water tight. The Triducer cable would also require a hole that I would seal with epoxy.

Has anyone done this, or something similar? I'd love any thoughts on this plan. My goals are to have a depth sensor forward of the dagger board, and away from any turbulent water created by the board or rudders. I want the unit in the water so I can take advantage of the speed and temp indicators.
Thanks
Wes
2004 M26

[Oskar 26M]

I have an Airmar P58 transom-triducer mounted on the starboard of my just under the boarding ladder. It's depth and temperature functions work great in that location. The log speed function also works very well when under sail or moderate power (up to about 8knots), but at WOT it picks up prop effects and indicates crazy speed (33 knots when the GPS tells me I'm making 14 knots).

Apart from the ever present leak hazards of any thru-hull (speaking from bad experiences on my previous boat), I wonder if the location you propose might cause some problems when launching or retrieving your boat. The triducer would have to protrude below the hull into the water flow if you wanted to get its log speed function to work and it would be easy to damage as the boat comes onto the trailer.

What about mounting it on your daggerboard? You would have to make depth corrections for daggerboard protrusion, but the triducer could be mounted so it can be retracted into the hull along with the board for launching and retrieval and there would be no hole in the boat .

[Gazmn]

Wes,

Please don't put a hole in the bottom of your boat

[David Mellon]

One of the features I like about The Yam is that it doesn't have any holes in it. Over the years I have had various types of hulls and the one thing that was my worst nightmare was a leak in the thru-hull fittings. I placed my transducer on the stern, port side, away from the boarding ladder to avoid kicking it off. I know it is the worst spot because of the prop effect. So far I have never seen any prop effect at speeds below 10 mph. Out in the deep blue at 19 mph I get all kinds of confused readings but I don't care. At that speed the only obstruction would be a submarine, whale or submerged cargo container but I would have passed it by before I could react. Besides at that speed I draw around one foot, I would see most objects from a distance because the seas would react to it. My advice is to not drill holes in a perfectly good hull, especially if you trailer the boat. Anytime the fitting interacts with the trailer you could easily shift it without noticing it. I say, don't do it!

[Hardcrab]

I'll go along with the others, and suggest against drilling the hull for a transducer.
Any hull breaching should be reserved for stuff that has zero options.
A transducer is not one of those.
You mention you want both forward of the dagger board and speed/temp.
I'd suggest you weed this choice down to one, and go with that.
There are many, many other options listed on this site to get either one, but not both.

If you still decide to have both, at least keep the hull hole in the ballast tank area so that any leaks will be contained.
You'll probally need to cut an access opening in the ballast tank to work on/seal the xducer installation.
A good sealed cover over the access hole should be easy to do.
Study it well before you start.

I'll chime in with an "in water" solution, not often mentioned here.
Mount it to the ballast dump valve.
No screw holes at all in the hull, just screw holes in the valve.
You'll need to be only slightly handy to make an interface mounting piece, but it's easy enough.

Mine works very well at that spot, except for higher motoring speeds (more than 10/12 kts) when the fish finder portion gets somewhat noisy.
The depth indicator and temp remains fine at any speed.
Under sail is never an issue.

[Mar de CaL]

Check out the Uniden 206 in hull , comes with a bath that adheres to inside of hull and 2 " digital display works at all speeds to 200 ft, bath or well installed behind battery compartment just to starboard , use fliud as suggested instructions to insure no freeze up.

[Divecoz]

I have Lowrance and its mounted under rear berth starboard side. Its a shoot thru / no holes . Its fine its great and no hole! I dont have or use water temp I need depth and really only at sailing speed . Why would anyone need or hope they can measure depth at high speed . By the time you see it its gone or damage is done. I agree with pthers here dont go drilliing holes you dont really have to, and Not below the water line / boot stripe.

[puggsy]

It would be wise to NOT put any holes in the hull. It is better to fit the transducer in a 'wetbox'' inside the hull., I described the construction of one some time back, using a short length of çost nothing'' 6 inch or more diameter PVC plumbing pipe. If you want a signal from in front of the dagger board, mount the box forward. The signal you will receive will be from immediately below the transducer. My Humminbird has a temp sensor, but you lose the benefit of this as it can only read the temp of the vegetable oil bath....in the box...in which the transducer is mounted. As for boat speed, the speed paddle is not as accurate as your GPS reading...It is your depth that is critical...Also, by being mounted inside, it is always fully protected from damage...
I am not able to get back on site for a week or more, if more info is needed...so check back on my previous posts on this subject,. Puggsy

[Oskar 26M]

Here is where i mounted mine:

[LOUIS B HOLUB]

I personally wouldnt want any "holes" anywhere, unnecessarily. I've had great results installing my transducer directly on the floor, under the galley sink. Using a large "glob" of silicone on, around, and on the bottom of the transducer works great. Just make sure there are no bubbles. Anyway, this installation prevents holes drilled, and the removal is simple if defects occur. (This installation is on my Mac-X).

My prev. boat, a Mac 26-S had the same installation done by a dealer, and it likewise worked well.

[Captain Kimo]

I have a Humingbird X100 fish finder and on a suggestion from this site, I set it in a heavy "glob" of plumber's putty just forward of the swing CB trunk in the bilge. Pushed it down flat against the bilge. The use plumber's putty was suggested in case the location was not optimal for getting a reading and the transducer had to be moved to another location.

It worked. Did nothing else with it and I has been functioning there for the last 7 years on my . Only draw back is the ballast tank has to be completely filled with no air bubbles to get a reading. It's not able to read beyond 400 feet (believe at that depth it starts to read the surface as 2 feet above the transducer, especially when heeled sailing), but my worries are the shallows and not deep water. I know that I am getting an accurate reading as I have touched bottom at 4 feet with the center board in a race trying to avoid an extra tack.

As with other, I don't recommend drilling any thru hull holes if you can avoid them .