I'm Giving Away Every transom mounted Transducer Setup Secret I Know — Here's the Complete Guide

April 28, 2026

19/06/26 FOREWORD : Im going to give you everything i possibly know about the subject on -How to position your transom mounted transducer for optimal results using the factory provided mounting. i want to provide a complete article that addresses everything in one hit, in order that you no longer need to continually look for answers in getting your transducer to read at speed. Below are principles which i think will aid you in getting better performance from your transducer. Among them will also be hints that ive discovered along the way.

After researching on this subject myself, i feel there is an element of secrecy as boaties want to keep some info to themselves because all aspects don't seem to be covered in How to articles? There are some good articles and videos but sometimes we need to know WHY we are doing something, we want to know the principle behind it so if our situation isnt the same as the video then we can make those changes knowing that we can adapt the information easily to our individual situations.

I will be constantly revising, editing and adding content to this blog as i too further learn, and remember aspects to cover, so keep coming back and checking. If something is off then i would appreciate it, if you let me know, so i can correct it and i am happy if you think something should be added. The ultimate will be a complete guide with pictures and will be easier to read but we shall get to that in time, in the meantime there may be something that will benefit you amongst the following info.

Reading can be boring so If needed, scroll past the section heading if you already have an understanding of that section, but be aware that if you really want to find that sweet spot then it is possible that your going to do have to do multiple on-water tests.

To get and maintain a good image on your fish finder at speed, It almost always comes back to turbulence and the transducer position on your boat .

The transducer is the part doing the real work — sending and receiving the sonar signal below the boat. But for it to do that job properly, a few fundamentals need to be right. Most people skip straight to height adjustment and wonder why nothing improves. The reason is simple —if the principles below haven't been addressed, then you will may only get partial results..

BEFORE WE START-WHAT SIDE OF MY BOAT SHOULD MY TRANSUCER GO?

Does it matter? a lot of opinions says it does BUT... Our article asks the question , WHY?... A: "because of prop noise!" As the prop digs into the water it throws water/wash out the other side[ depending on rotation] all into the transducer "zone"

Does that makes sense ? When the boat is moving forward under speed , how can turbulent noise from the prop wash travel forwards? The boat is moving away [ forwards] all the time from any water disturbance created by the propeller, isn't it? Think about it ,go out to your boat, trim your motor down and visualize that scenario.

Yeah the prop will disturb water around the prop and more so on the outward side of the prop digging action sending the wake/ wash sideways out towards the port side [ if the prop rotates clockwise] but have a look on your boat from the side and behind and imagine how much the disturbed water would have to travel to get to where your transducer generally sits, and then imagine the boat travelling forwards with water pressure sending the disturbance wash backwards and away. Have a look at my main pic on heading of this article [and pics below], look how far away the transducer would be away from those forces and then look at a side image, the prop is a lot lower than where a transducer is usually located. Have a look on You Tube by searching "propeller rotation under water", and you will see the turbulence coming off the blades but the turbulence does not travel forward or sideways when the boat is travelling forward.

So choice is yours, starboard is obviously better [with a clockwise spinning prop] but have a look at your scenario after what's been discussed if it has to go on the port side for any reason.

The only thing left that could be possibly be an issue that is mentioned loudly would be the electromagnetic field emanating from the motor, however...

1. Where EM fields are actually generated

The strongest EM activity in an outboard motor comes from the ignition system (spark plugs, coils) and the alternator/stator near the powerhead (top of the motor).
These components generate changing electrical currents, which naturally produce electromagnetic fields.

2. What’s in the lower section

The lower unit (gearcase) mainly contains mechanical components: gears, shafts, bearings, and the propeller.
There are typically no active electrical systems down there, so it doesn’t intentionally generate EM fields.

3. Any EM presence in the lower unit?

Very minimal, indirect effects only:
- Metal parts can conduct or slightly interact with EM fields generated elsewhere in the motor.
- If the motor has sensors (some modern ones do), there might be very weak localized electromagnetic activity, but nothing significant.
In general, it’s negligible compared to the upper engine components.

4. Exception cases

Some modern or specialized marine systems (like electric outboards or advanced sensors) may introduce wiring or electronics lower down—but even then, EM emissions are still relatively low.

Bottom line:
The lower section of a typical outboard motor does not meaningfully emit electromagnetic fields. Any EM activity is overwhelmingly generated in the upper engine area, not the gearcase.

I've been working on boats long enough now that I've seen hundreds of scenarios whereby the transducer is on the port side and there has been no issue at all.

HINT# Also consider that It is also not recommended to cable tie cables [from other transducers , light, pumps etc] to your transducer cable as it will possibly pick up EM fields from those other electrical devices. RUN the transducer cable SEPRATELY for best results.

Principle 1 — Get your transducer as close to the keel as possible.

The keel is the lowest point of your hull and the place where the water flowing beneath your boat is at its cleanest and most stable. The closer your transducer sits to the keel, the better the signal —less turbulence and better the image.

Boats have a V-shaped hull — deep and shallow. As your speed increases, this V shape hull is designed to lift and plane off the water, reducing friction. As the hull lifts so does the transducer. Along with the boat listing [seesawing] from side to side, a transducer will send sonar out at an extreme angle but may not receive the sound back, add a bit of chop - image lost, and a transducer mounted too far out towards the gunnel can break the surface and lose contact with the water entirely. At that point your image goes to fuzz.

Mounting as close to the keel as possible keeps the transducer in the water and in contact with the cleanest, most stable flow — even at speed, even when the boat is on the plane.

Your transducer cannot sit in line with the propeller. The turbulence created by the transducer moving through the water will interfere with prop performance. To check this, trim your motor through its full range and visualise that any upstream turbulence from the transducer doesn't trail toward and enter within the propeller's diameter. Get the transducer as close to keel as possible BUT outside of the prop diameter.

ATTENTION# You also need to check your motor at full turned lock — both directions — and confirm that throughout the entire trim range, the outboard cannot make contact with the transducer at full turn.

Principle 2 — Know where your strakes are.

If your hull has strakes — those raised ridges that run along the bottom of the hull — your transducer position relative to them matters more than most people realise.

Strakes tear up the water surface beneath them, creating aeration in the water layer directly behind them. A transducer sitting in that aerated stream is fighting a losing battle — no matter how good your sonar unit is, it can't produce a clean image through disturbed, bubble-filled water.

The goal is to position your transducer between the strakes, where the flat section of the hull produces significantly less disturbance to the water flow.

Some strakes don't run the full length of the hull — they stop short of the transom by around a metre or so. In that case the turbulence they create may dissipate somewhat before it reaches your transducer.

If you're unsure of their impact, have someone look over the back of the boat while you're underway. Look for the water streams coming off the transom area and find where the flow is cleanest and least aerated. That's where your transducer wants to be.

ATTENTION# - Along with strakes there should be nothing upstream and inline of the proposed transducer position such as inlets / outlets , thru hull fitting etc - these will cause a turbulence trail, even if they only stick out slightly.

Aluminium Boats - If you have a pressed hull type, with pressed strakes running parallel along the length of the boat at very close intervals, then as mentioned above, these strakes tear up the whole top surface of water compared to a plate boat [with less strakes] so each strake is ripping up the surface water that, when your transducer is skimming will be then trying to read through this aerated surface layer. Your pressed aluminium hull is designed to give the hull strength[ because it's usually thinner aluminium] , and when it gets on the plane , it lifts the boat out for performance as mentioned above so what you might find is that your transducer may need to run deeper if you have this type of hull.

Keep in mind too that your transducer shape can have a big impact on results with your pressed hull. Compare having the large brick -like shape of the 1KW transducer to a skinny and thin streamlined Garmin GT or Lowrance 3-1 transducer. The large bulky shape of the 1KW may be a challenge to achieve excellent results with a pressed hull simply because of its size, so be realistic and hopefully you have considered this aspect before you go out and buy a 1KW for your pressed hull.

HINT# The way in which the Aluminium transom is welded to the hull can have an effect on the water "cleanliness" that emerges from under the hull. Usually the hull is welded to the transom using a mig welder which can leave the weld bulky with excess weld material on that join. This bulky weld tears up the water causing aeration through which the transducer then has to read through and you can lose the quality of your sound as you increase in speed. You can sand this join to remove the excess weld material to make the weld smooth in the area where the transducer is to be located between the strakes. BUT you have to ensure its done carefully to ensure you leave enough weld to not weaken the join, ensuring the join holds together or you can cause the area to split and therefore leak water in and you will have to get it rewelded. The high weld beads can at least be sanded down. Use 100-180 grit to start with then up to - 400 grit to finish with some lubrication or soap and the sanded area will be smooth. The goal is to keep the fast water as smooth as possible.

Principle 3 — Don't trust your welded transom plate.

If you're running an aluminium boat with a welded transom plate, don't assume it's in the right position just because it's permanently fixed to the hull.

The person who welded that plate on was a skilled fabricator — but understanding the principles of transducer placement is a completely different discipline. In most cases they were told "sort of" where to put it and welded it on.

Boats of an older age will sometimes have transom plates that were designed to accommodate the older style of transducers and when they were installed the idea of reading at speed wasn't a big thing as it is today so be wary, you may need to consider modifying or welding on a new plate. OR as mentioned later, remove it completly.

Before you accept that your welded plate is in the optimal position, apply the same principles from Steps 1 and 2. Is it as close to the keel as possible? Is it clear of strake turbulence? Is it clear of prop wash? Is it safe through the full trim and lock range of your motor?

Principle 4 — Your transom plate design could be working against you.

A welded transom plate gives you a sacrificial surface to drill into without touching the transom itself — that's a legitimate benefit. But the design and position of that plate can quietly cost you sonar performance.

The plate may be bringing your transducer too far from the transom.

Every millimetre you move away from the transom introduces more disturbed water. A transom plate that projects 20mm or more out from the hull adds exactly that distance plus the factory mounting distance — and that gap introduces air into the system that directly degrades your sonar image.

The ideal setup is no transom plate at all — transducer mounted directly against the transom. If drilling into your transom and sealing holes isn't something you're comfortable with, a thin, [ not thin material] well-positioned plate is the next best option. But understand that every millimetre of gap has a cost. Tig integrity mounts are designed to compensate for this.

The plate may be positioned too high.

Some transom plates incorporate angled folds at the lower edge — which effectively raises the flat mounting surface higher on the transom. The result is that your transducer can't get low enough to skim the waterline properly. If you try to compensate by forcing the transducer deeper with a factory mount, the rear of the mount ends up exposed to fast moving water — creating its own turbulence and making the problem worse. You may notice that the simple image you get in the manufacturers instructions is not the same as your scenario.

Tig integrity mounts are designed to give you that extra depth to compensate for the high transom plate.

Principle 5 — Transducer height.

The standard recommendation is to run a straight edge along the hull bottom and position the transducer so that its straight edge line sits approximately halfway through the thickness of the transducer. It's a reasonable starting point — but the diagrams in the manual are generalised and drawn for an idealised scenario that may look nothing like yours.

Some confusion comes from which side should i do this from? if your transducer is positioned on the starboard side then you would do this exercise from the starboard side of the transducer - the side that is most exposed to the water coming under the hull. [reverse image if transducer is located port side] Remember standard transducers send out a cone and part of that cone needs to "see" slightly under the boat, even a little in front of itself and so if its too high and tucked behind the transom it cant "see" forward at all.

The ideal — skim the surface.

The best possible scenario is a transducer set to skim the very top layer of the water. As you know there are many boats that get great results with the transducer set up like this.

The problem is that as your boat accelerates and gets up on the plane, the hull lifts — and the transducer lifts with it. A transducer that was perfectly placed at rest can come up and out of the water at speed. So that may not work for your scenario, That's 3/4's of my customers, they don't get a quality read when "skimming"

When skimming doesn't work — go lower.

If you've experimented with height and still can't get a consistent read at speed, the answer is to go lower. Getting the transducer deeper into the water keeps it in contact with the water through the hull's lifting motion and gives you a more stable signal across a wider speed range.

This is where most people hit a wall. They've run out of adjustment on their factory mount — and that's not a technique problem. That's an equipment limitation.

Major point-I've been doing this for a decent amount of time to see a lot of different scenarios as people send me photos of their set up with the issue they have and a lot of the time i see photos of their transducer set up too deep using the factory mount. They have the lower corner of the rear fixing plate in the fast water [ below the hull line]or the rear [radiused or rolled section] of the transducer footprint plate [ the plate where the transducer is screwed to ] below the transom plate or below hull line- in the fast water. This will 100% of the time cause issues because those 2 sections smash against the water and cause turbulence.

That why TI mounts have longer arms so that you can get deeper without the rear plate digging into the water and there's no part of the mount that smashes against water [ except the thin side arms]

Principle 6 — Transducer angle- its just physics.

Most transducers are long, thin and low in profile — designed to streamline through the water with minimal resistance. But that streamlining only works when the transducer is running parallel to the water surface. Put any angle on it at speed and it's creating resistance, turbulence, and degrading the signal.

The goal — You want to achieve that the transducer is parallel to the water at the speed you reasonably expect to find new spots, see a clean bottom contours and see fish at.

Not parallel to the boat at rest. Parallel to the water at the speed you want to be reading at. Your aim is to set the transducer at home so that when you're out on the water at your designated fishing speed, the transducer face is running level through the water at the speed your wanting. I keep repeating this as this is how we need to understand it.

If you have an angle finder at home you can go out in the boat ,set it on a straight surface such as the side of the boat, when doing the expected speed you want to read at, record the angle. When you get home, recreate the angle on your boat you were running at [using the jockey wheel and possibly a jack] , then level your transducer with a spirit level.

So effectively what your doing is ensuring that the transducer is running parallel with the water [ as water is true level] when you are at the expected speed.

IMPORTANT TO CONSIDER # - Find your base angle.

Your boat is never at a fixed angle — speed, motor trim, wind, chop, and load all shift it constantly. Add to that the fact that every hull is different: some boats ride bow-high, others push the nose down under load or at certain speeds. There's no universal "correct" angle.

What you need is a base angle — a consistent reference point you choose based on your boat, your typical fishing speed, and your average water conditions. Once you've established that baseline, you adjust your transducer angle from there.

Think of it as dialling in for your most common scenario, not every possible one.

No angle finder? Search YouTube for "how to level your transducer with a level and coins" — it's a simple method anyone can do. I've watched these videos but they always mention to do it at rest, however your boat will be at a different angle when its underway. An angle finder is better as coins or washers will go everywhere if your at a little speed . If you want further info Send me a message or i have a detailed video on this subject in my How to videos.

So where does that leave you?

So You've worked through every principle- Position on the transom. Strake turbulence. Transom plate design. Height. Angle. ETC.. You've considered all of it and made every adjustment available to you. BUT.....

If you still want better results or the results still are not satisfactory, there's only one place left to go.

Deeper.

Because deeper is where the water is clean. Below the surface turbulence, below the aeration, below the disturbance created by the hull moving at speed — down there the water is stable, undisturbed, and perfect for sending and receiving a sonar signal. It's where your transducer has always wanted to be.

The problem is getting it there.

Think about your propeller, how deep is that positioned to dig into the cleanest water? You don't want your transducer to be down there but the point is , that deeper is undisturbed water. Some who want better sonar performance are not going to find that sweet spot, skimming surface level in the turbulent water.

A factory mount wasn't designed for depth. It has a fixed range of adjustment, limited depth capability, and at greater depths the pressure and drag exerted on the mount at speed becomes more than it was built to handle. You also want the transducer as close to the transom as possible — because distance from the transom means more turbulence, and more turbulence means a degraded image.

This is the gap that TIG Integrity products were specifically built to fill.

Our range of transducer mounting solutions are designed to get your transducer deeper, closer to the transom, and held firmly in position under the pressure of real fishing speeds. They're built for the conditions a factory mount was never intended to handle — and they're the logical next step for anyone who has worked through these principles using the factory mounting and found themselves out of options or not seeing improved results.