Trawlers and Transom Mounted Transducers

[Redhook98]

I picked up a Defender special consisting of a factory re manufactured Raymarine Axiom 9RV with a transom mount RV-100 transducer included. Too good of a deal to pass up at $699, and it will sit nicely next to the other Axiom 9 I have mounted in the pilothouse.


Anyway, I read a few threads on here about other trawlers having transom mounted transducers and not having any issues. Any with twin motors? Issues at different speeds (my max is 8 knots)? Or better off to fabricate an in-hull mount for it?



I have two older Garmins that are going to act as my primary depth finders using P79 in-hull transducers.

 

[Solly]

I just did this last year. Axiom MFD and the RV 100. All I was looking for was depth under the keel. Wasn't real interested in fish or bottom structure.
Epoxied the transducer to the inside of the hull next to a stringer. Works very well !! I was really surprised ! No idea if it's degraded or not but I didn't want to put holes in the transom.
Take the transducer and submerge it in a plastic bag of water in the location you want to put it and try it out. Have to hold it in position under the water.
I mixed up some West epoxy with enough filler to keep it from running. Lightly sanded the hull where it was going to sit. Put a big glob of epoxy in the space between the stringer and hull. Set the transducer in the epoxy and wedged it in place until the epoxy kicked. Filled up probably halfway up the side of the transducer. And make sure there are no air bubbles or voids in the epoxy.

 

[Comodave]

Just don’t use silicone to stick it to the hull, it supposedly weakens the signal.

 

[caltexflanc]

I know people who have installed simple Humminbird depth systems with transom mounts, you just want to be as clear of propwash as possible. One trawler guy attached it to the side of the boat, aft, instead on the transom. Rather than screw it in, use 5200. Run the cable externally. Mind the installation instructions in the owner's manual. These all are designed to work on boats that go a lot faster than 8 knots.

 

[Redhook98]

I just did this last year. Axiom MFD and the RV 100. All I was looking for was depth under the keel. Wasn't real interested in fish or bottom structure.
Epoxied the transducer to the inside of the hull next to a stringer. Works very well !! I was really surprised ! No idea if it's degraded or not but I didn't want to put holes in the transom.
Take the transducer and submerge it in a plastic bag of water in the location you want to put it and try it out. Have to hold it in position under the water.
I mixed up some West epoxy with enough filler to keep it from running. Lightly sanded the hull where it was going to sit. Put a big glob of epoxy in the space between the stringer and hull. Set the transducer in the epoxy and wedged it in place until the epoxy kicked. Filled up probably halfway up the side of the transducer. And make sure there are no air bubbles or voids in the epoxy.

I'm guessing the only real downside is it's now there for the life of the boat? How does the picture look? Still have good bottom detail?


Has anyone ever cut one of the transducer cables in order to run it, and then re-spliced? I have to go up a pretty crowded pipe from the lower helm to the upper helm. That's a big plug.....

 

[ImaBoat]

Watching thread.....also interested

 

[Pau Hana]

We've used a P-79 in hull transducer since 2012. Zero problems, and we regularly see depths of over 400'.

 

[Solly]

I'm guessing the only real downside is it's now there for the life of the boat? How does the picture look? Still have good bottom detail?


Has anyone ever cut one of the transducer cables in order to run it, and then re-spliced? I have to go up a pretty crowded pipe from the lower helm to the upper helm. That's a big plug.....

Always figured I could cut it out if needed. Probably destroy the transducer but nothing structural to the boat. Use a multi-tool and cut on the sides and bottom thru the epoxy.

Detail is fine for what I want. I can see some detail of the bottom but no idea on any difference. Fish show up. Big thing for me also was no interference from the wake or goop growing on the transducer. And like i said, no holes into the fiberglass.

Raymarine has a good forum. I'd ask on there b-4 cutting any cables.
I'd recommend against it without getting their opinion.

 

[koliver]

I bought a Humminbird sounder/plotter 10 years ago. came with a transom mount T-Ducer. I stuck the T-Ducer in a blob of epoxy in the bottom of the inflatable, a foot or so away from the transom. It helps me get prawns, so I need a reliable reading down to 600'. It gives me that.
I subsequently bought a kit so that I could also mount it on the Trawler FB. Again came with only a transom mount T-Ducer but too short a cable to reach. I epoxied a 3" ABS pipe to the inside of the hull within a foot of my wheelhouse sounder's T-Ducer, attached the transom mount T-D inside the pipe and Bob's yer Uncle. Again good service for 10 yrs, down plenty deep enough.

 

[PM]

Transducers have come an awfully long way in the past 20 or 30 years. In the olden days they wouldn't work through the hull and didn't work very well with turbulence.

All that has changed!

pete

 

[Mrwesson]

Just don’t use silicone to stick it to the hull, it supposedly weakens the signal.

I have 2 different transom transducers mounted with silicone and haven't noticed a difference. One of the units was off my fishing boat and used in the same area. Picks up the bottom all the same.

I'm sure there's some truth to it but when your system is on auto the gain is typically very low and I assume the unit just turns the gain up enough to get the same results. None of these systems are running at 100% gain and if needed I'd bet they'd shoot through a 3" thick hull.

I could be wrong though.

 

[Scottwb96]

I have that exact setup on my boat. Works well through all speed ranges (1-20 knots)... Even when I kick on the thruster, the turbulence doesn't seem to effect it. That transducer is amazing, I wouldn't mess with the structural integrity of it. If you want a different mount, sell it and get the one you want!

 

[Redhook98]

I found a spot install inside the ER. I layed down a layer of Epoxy to make it flat. After it dried, I filled a bag with water and put the transducer in it. My slip is only about 6 feet deep and the reading on the Axiom was about 4.5 to 5 feet (position of transducer is about 1 ft below water line). I was able to see a very very limited pic as there really is not enough depth right now for a good picture to develop.


If I am getting depth and see the start of a picture, is that an indication that the position I selected is OK to use? What do I want to see on the display to confirm it is a viable spot for install.

 

[Redhook98]

I have that exact setup on my boat. Works well through all speed ranges (1-20 knots)... Even when I kick on the thruster, the turbulence doesn't seem to effect it. That transducer is amazing, I wouldn't mess with the structural integrity of it. If you want a different mount, sell it and get the one you want!

That is a nice, clean install. Not yet sure if I am going for an in-hull or transom mount yet though. I want to see how the in-hull tests work out first.

 

[GoneDiving]

Bringing an old post back to life to see if anyone had any issues from extending cables on a transom mount finder/down scan?

I'm attracted by the Lowrance Hook and Reveal range and called them about the maximum cable cable length. They recommended only one 10ft cable extension. Apparently any more results in a drop in resolution. I would need ~40ft for a 54ft vessel.

Has anyone significantly extended transom mount units? How has this affected performance?

I'd expect one spliced extension to perform better than numerous OEM 10ft extension leads??

FWIW I'm a diver who doesn't know how to bait a fish hook so I'm looking for gross resolution that identifies underwater wrecks or drop offs and general bottom depth details rather than fine fish location details.

Many thanks.

 

[CTP]

I have a couple questions...

Epoxied the transducer to the inside of the hull next to a stringer. Works very well !!

I have questions!!! I got the same system and wondered if this was possible before I went spending the money on thru-hull transducers and the labor to install them.


Where exactly in the boat did you install it? I assume it's epoxied in level with the water, and not the slope of the hull? I have a nice spot dead center but I don't know how thick the center of the hull is there...guess I need to run some tests!


Thanks!

 

[Solly]

CTP I installed it in the engine room beside the engine. Had an open space on the outside of the engine bed stringer. First put it in a bag of water to see if I could get a picture. It did so I epoxied it in place.

 

[CTP]

Wow, this is fantastic! I cannot wait to try it out.


Thank you!