Transducer installation query

[isljam]

Hey folks.
I am doing my first transducer install on my 4.5m Aluminium Brooker runabout and need a little advice please.
I’m aware I need to choose a flat, unobstructed point on the transom to mount. Avoiding chines, welds and hardware etc, to ensure unobstructed water across the transducer.
The concern is that the weld along the bottom of the transom creates a small ridge. So, running along the hull it is smooth until it meets the transom. There, the water would have to travel over the small ridge created by the weld. The manual for the unit recommends mounting 10mm below bottom of hull.
Is this going to create a disturbance in the operation or the transducer. Of course, there is no way to avoid it as the weld runs the entire length along the base of the transom.
Should I attempt to file / sand this weld line flat or could this jeopardize the integrity of the weld?
Thanks

 

[dingbat]

The concern is that the weld along the bottom of the transom creates a small ridge. So, running along the hull it is smooth until it meets the transom. There, the water would have to travel over the small ridge created by the weld. The manual for the unit recommends mounting 10mm below bottom of hull.
Is this going to create a disturbance in the operation or the transducer. Of course, there is no way to avoid it as the weld runs the entire length along the base of the transom.
Should I attempt to file / sand this weld line flat or could this jeopardize the integrity of the weld?

Transom mounts are always problematic in this regard thus the popularity of in-hull and thru-hull applications

Having said that, are you using it as a "depth gauge" or a "fish finder"?
Big difference in the "quality of the mount" required for both applications

 

[JimS123]

10 mm below is going to cause a roostertail. You might not like it. OTOH, that might just be low enough that the weld won't bother you.

Most mounts are adjustable up and down. Try it, adjust it, set it where you get good results.

I have a chirp transducer on one boat, factory mounted, and it's quite low. Splashes a lot but has awesome performance. Any 'ducer that I ever personally mounted was flush with the bottom. But I never had a weld, at worst just a row of rivets.

 

[Texasmark]

Why don't you mount it inside the boat at the transom, near the keel just in front of the disturbance assuming you have clean solid material (no foam, no balsa, solid epoxy glue with bubbles minimized) If you have a dead rise at the transom use a thick layer of epoxy to get a solid triangular base for mounting it vertical. You can build forms for the epoxy with cardboard and tape. Bury the ducer in the epoxy enough to ensure good contact. Been that way my last 3 boats and not about to change.

 

[JimS123]

Why don't you mount it inside the boat at the transom, near the keel just in front of the disturbance assuming you have clean solid material (no foam, no balsa, solid epoxy glue with bubbles minimized) If you have a dead rise at the transom use a thick layer of epoxy to get a solid triangular base for mounting it vertical. You can build forms for the epoxy with cardboard and tape. Bury the ducer in the epoxy enough to ensure good contact. Been that way my last 3 boats and not about to change.

I realize lots of people do that and are satisfied. But, have you tried it both ways and compared performance? It just seems to me that the hull and epoxy would somewhat reduce sensitivity.

 

[dingbat]

I realize lots of people do that and are satisfied. But, have you tried it both ways and compared performance? It just seems to me that the hull and epoxy would somewhat reduce sensitivity.

Experimented quite a bit on my last boat.

Couldn’t not for the life of me to get a transom mount to run clean. Didn’t want to install a thru-hull so I started exploring shoot thru installations.

After experimenting with a couple of different installation methods, epoxy shelf, flat spot, etc. I ended up with a Airmar P79 install.

Introduced a 40% lose of power and sensitivity but gave good performance on a 600W unit. Wouldn’t do so well with a lower powered sonar unit.

Went thru-hull on current boat with side scan on the transom. Best of both worlds

 

[isljam]

Transom mounts are always problematic in this regard thus the popularity of in-hull and thru-hull applications

Having said that, are you using it as a "depth gauge" or a "fish finder"?
Big difference in the "quality of the mount" required for both applications

Can you elaborate please? I want to use all the features of the sounder to find structure and ultimately fish. Combination of 2d sonar, Down Scan up to 1000khz and side imaging. Have a lot of learning and experimenting to do, but just want to get the installation right first.

 

[isljam]

Why don't you mount it inside the boat at the transom, near the keel just in front of the disturbance assuming you have clean solid material (no foam, no balsa, solid epoxy glue with bubbles minimized) If you have a dead rise at the transom use a thick layer of epoxy to get a solid triangular base for mounting it vertical. You can build forms for the epoxy with cardboard and tape. Bury the ducer in the epoxy enough to ensure good contact. Been that way my last 3 boats and not about to change.

Thanks Texasmark:

This is my first install and have to say that sounds a little complicated. Not 100% sure what you are describing. Building a flat bottom on the hull to the transom with epoxy?
The boat is a 4.5m runabout with wooden floor. The rise is only a mm or 2. The thickness of the weld.

 

[isljam]

Experimented quite a bit on my last boat.

Couldn’t not for the life of me to get a transom mount to run clean. Didn’t want to install a thru-hull so I started exploring shoot thru installations.

After experimenting with a couple of different installation methods, epoxy shelf, flat spot, etc. I ended up with a Airmar P79 install.

Introduced a 40% lose of power and sensitivity but gave good performance on a 600W unit. Wouldn’t do so well with a lower powered sonar unit.

Went thru-hull on current boat with side scan on the transom. Best of both worldsView attachment 357570

Hmmm... Not sure how this would work with my Garmin GT56 UHD transducer?

 

[dingbat]

Hmmm... Not sure how this would work with my Garmin GT56 UHD transducer?

It will not work. GT side scan has to be on the transom.

 

[dingbat]

Hmmm... Not sure how this would work with my Garmin GT56 UHD transducer?

And be forewarned that the location noted in the install manual isn’t negotiable. Too far off center line and the side scan beam hits the lower unit, cutting off the picture.

One other thing…did the unit come with a spray shield for the transducer?
Unless they redesigned the mount, which it doesn’t look like, you will need one to keep the spray down. Spray is bad while running even with the shield.

 

[Texasmark]

Thanks Texasmark:

This is my first install and have to say that sounds a little complicated. Not 100% sure what you are describing. Building a flat bottom on the hull to the transom with epoxy?
The boat is a 4.5m runabout with wooden floor. The rise is only a mm or 2. The thickness of the weld.

Cured rosin or aluminum are solid substances that absorb and retransmit sound waves very well. Wood would probably be a bummer for a couple of reasons. Acid test would be to go some place where you frequent....know that you will be looking for targets in the area...... and hold the ducer overboard where you would mount it externally. Find a weak target for visual fixation with a given gain setting on the receiver.

With a gallon size (for a number) zip lock bag of water sitting on the hull where you would mount it internally, submerge the ducer in the water and recheck your reference point. Obviously it will be weaker but how much....increase your gain and see if you recover the reference point. If so, go for it.
Your bottom is flat enough for a thin layer of epoxy and depress the ducer till it bottoms out.

Obviously a side scan system is blocked by the hull.

 

[JimS123]

And be forewarned that the location noted in the install manual isn’t negotiable. Too far off center line and the side scan beam hits the lower unit, cutting off the picture.

One other thing…did the unit come with a spray shield for the transducer?

Aha! Never heard of that before. I just looked up one for my Raymarine chirp downscan and the cost was outrageous. After all, the spray is out back and it really doesn't hurt anything.

Nevertheless, it piqued my interest. Are there low priced generic models available?

My SeaRay has a factory mounted thru-hull right on the keel. The hull is molded just for that install. Best setup ever.

 

[dingbat]

Aha! Never heard of that before. I just looked up one for my Raymarine chirp downscan and the cost was outrageous. After all, the spray is out back and it really doesn't hurt anything.

Not on any Garmin units I've seen......it shoots out the sides of the mount.

Drowns the side of my motor like in the video. Worried about taking out my trim buttons on that side.

Nevertheless, it piqued my interest. Are there low priced generic models available?

I was one of the early guinea pigs.... No such thing available commercially at the time. Garmin sent me a template of the prototype and I made my own out of 0.06" stainless. Spent way more than $25 in material, time and effort.

My SeaRay has a factory mounted thru-hull right on the keel. The hull is molded just for that install. Best setup ever.

I wasn't aware that anyone made a side scanning transducer in a single, thru- hull mount?

The only thru-hull SS transducer I'm aware of require two transducers, one on each side of the keel

How do they keep prop wash from interfering with the signal? My CHIRP (B75M) thru hull is mounted on the keel 20" fore of the transom.

I don't look at the display anytime the motor is in reverse

 

[JimS123]

I wasn't aware that anyone made a side scanning transducer in a single, thru- hull mount?

The chirp is a transom mount on my Whaler. The thru-hull on my SeaRay is not. I was just commenting how well a thru-mount works.