Fish finder - transom mount OR thru-hull?

[7lazy77]

I have a 25' deck boat & would like to install a fish finder on it. I know it is not the most ideal fishing boat, but it is a compramise for our multiple uses. I am not sure which would be better, a transom mount or thru-hull? Anybody out there with bigger boats that have a fish finder?

 

[JoLin]

Re: Fish finder - transom mount OR thru-hull?

IMO it's six of one, half dozen of the other. My boat came with a (now faulty) thru-hull depth finder. When I upgraded the boat's electronics I installed a ff with a transom mount transducer. It works.

 

[gm280]

Re: Fish finder - transom mount OR thru-hull?

This is a good question. I've always wondered if there is any degradation installing a transducer inside a fiberglassed haul as opposed to mounting one on the exterior transom. Maybe someone will come on here and give some insight to capability with both locations with same system and transducer...

 

[dingbat]

Re: Fish finder - transom mount OR thru-hull?

Thru hull advantages:
1. Surface clutter is reduced or eliminated
2. Transom rot is not an issue
3. Reads at speed
4. Nothing hanging off transom to get broken or damaged
5. No cable to route over or thru transom
6. Typically, a better sensor


Transom mount advantages:

1. Easy install
2. Typically lower cost sensor

 

[cjjjdeck]

Re: Fish finder - transom mount OR thru-hull?

I have two transducers in my boat. One unit is a factory installed in-dash unit with the transducer installed on the interior of the hull (not through the hull). The factory mounts this near the bilge pump just ahead of the engine. I wanted this unit as a back-up to my Fishfinder/GPS Chartplotter unit.

The other is a transom mount for the Fishfinder/GPS Chartplotter.

I frequently look to see if there is a difference in the readings between the two. Rarely has there been a difference in the readings (maybe a tenth of a foot only if off at all). Faria makes the in-dash unit and Lowrance makes the transom mount unit. I honestly can?t tell you which is better since they have both performed pretty much the same at trolling and planning speeds. I know this isn't exactly a perfect comparison since the two sonars are of different manufacturers, but this has been my experience.

 

[gm280]

Re: Fish finder - transom mount OR thru-hull?

I have two transducers in my boat. One unit is a factory installed in-dash unit with the transducer installed on the interior of the hull (not through the hull). The factory mounts this near the bilge pump just ahead of the engine. I wanted this unit as a back-up to my Fishfinder/GPS Chartplotter unit.

The other is a transom mount for the Fishfinder/GPS Chartplotter.

I frequently look to see if there is a difference in the readings between the two. Rarely has there been a difference in the readings (maybe a tenth of a foot only if off at all). Faria makes the in-dash unit and Lowrance makes the transom mount unit. I honestly can’t tell you which is better since they have both performed pretty much the same at trolling and planning speeds. I know this isn't exactly a perfect comparison since the two sonars are of different manufacturers, but this has been my experience.

I'm a bit confused now... You stated that you had one transducer in the interior of the haul but not through the haul. How does that work or is setup. I just don't understand that setup. I'm trying to decide whether to mount the transducer inside the haul and epoxy it to the haul OR transom mount like usual...

 

[cjjjdeck]

Re: Fish finder - transom mount OR thru-hull?

I'm a bit confused now... You stated that you had one transducer in the interior of the haul but not through the haul. How does that work or is setup. I just don't understand that setup. I'm trying to decide whether to mount the transducer inside the haul and epoxy it to the haul OR transom mount like usual...

I apologize for the confusion. I was attempting to make sure you understood which type of in-hull mounted transducer I have in my boat and didn't do a very good job.

There's one type that you epoxy to the interior of the hull (which is what I have) and another design where you drill a hole through the hull so that the surface of the transducer protrudes through the hull and is actually in the water.

 

[gm280]

Re: Fish finder - transom mount OR thru-hull?

I apologize for the confusion. I was attempting to make sure you understood which type of in-hull mounted transducer I have in my boat and didn't do a very good job.

There's one type that you epoxy to the interior of the hull (which is what I have) and another design where you drill a hole through the hull so that the surface of the transducer protrudes through the hull and is actually in the water.

Ha thanks for the clarification. I do understand what you are saying now. So you are using an epoxy type transducer and not having any problem. Thanks for the info. It goes a long way to help me figure out what I want to do... Have a great day... :joyous:

 

[cjjjdeck]

Re: Fish finder - transom mount OR thru-hull?

Yeah, the terminology can be a bit confusing. The transducer manufacturers (like Airmar) describe "In-hull" transducers as the type you're interested in (and the one I have) and "Thru-hull" as the style designed to protrude through the hull requiring drilling through the hull to mount. Thru-hull models can have units that embed in the hull and it's surface is pretty much flush with the bottom of the hull, or surface mounted models.

I'm actually glad I have the in-hull. Besides having it as a back-up, I keep my boat in a slip all season and to prevent theft, I take my fishfinder/GPS chartplotter with me whenever I'm coming to or leaving the marina. Sometimes we just want to cruise familiar water and having the in-dash sonar allows me the option of saving a bit of pre-launch time by not having to hook up the other unit for this type of use.

Good luck with the install!

 

[dingbat]

Re: Fish finder - transom mount OR thru-hull?

I've always wondered if there is any degradation installing a transducer inside a fiberglassed haul as opposed to mounting one on the exterior transom. Maybe someone will come on here and give some insight to capability with both locations with same system and transducer...

The depth reading is a time based so you will see very little, if any degradation of the accuracy of the depth. Some will argue that depth is slower to update but that has no basis in fact.

What is affected is the max depth the unit can read and the unit’s sensitivity.
The loss of signal from passing thru the hull will have a minimal impact on the unit’s maximum deep capability. Your maximum depth may go from something like 500’ to 475’ ft. depending on the material and the thickness your shooting thru. You can make you some of it by increasing your gain, but all that does is amplify the already derogated signal.

On the other hand, the signal passing thru the hull will have a major impact on the unit’s ability to “see” individual objects.
A transducer is designed to “listen” specific range of frequencies. Anything outside that frequency range is ignored. As the signal pass thru the due hull of the boat, the material induced a frequency shift of the sonar beam. Depending on the type and thickness of material, the shift and the associated "blindness" can be considerable.