FACT:  Hull design, make or model of your boat has little, if anything, to do with any more or less "turbulance" or disturbed water any more than one design over another. They all create a mess! So, hanging over your transom to locate the "smoothest water" at 40 mph is just plain poor judgement. Follow the Rules and avoid the catastrophe.

FACT:  Flat bottom skiffs do not "trap more air" than other hull designs. In fact, flat bottom skiffs actually have less wetted surface than comparably sized V hulls.  No one type hull "traps" more or less air than the other.

Slick gel coat or rivets...smooth, bubble-free water does not exist behind any fast boat...DEEP V or Flat-bottomed Skiff makes no difference.  If you have heard that it does, that is malicious advice.  Don't look for it! We've heard for years that the elusive smooth, turbulent-free water is back there somewhere. Those that are so quick with the "smooth-spot" advice all seem to quickly disappear when asked about it.        
Problem: The black and white diagram of "a boat at speed" is intended to demonstrate water flow created by a fast moving boat and across the face of a transducer. The black and white illustration (above) is inaccurate for anything except maybe a slow drifting boat, but has been widely used for many years to teach the proper adjustment of a transom-mounted transducer for correct high speed use. What really happens? Dragging a trailing transducer mounted closely to the transom and below the hull (in the "trough") of a boat, forces a powerful flow of already disturbed water into, around and over the transducer creating all sorts of sounding chaos. We have accepted this as customary for transom-mounted transducers, simply because this is what we've been instructed to do...and do our best to deal with it. We have learned, that by moving the transducer aft, and by adjusting it upward toward the elevating slipstream, will afford a corrective advantage toward optimizing your high speed transducer sounding. 

Correct the Problem! Nature provides a subtle solution. We simply failed to recognize it. A typical planing or fast moving displacement hull creates stern squat (weight and thrust) and bow rise which dramatically changes the movement and dynamics of the water differing significantly from the B&W line illustration. This action thrusts the transducer deeper...much deeper than you might realize or have thought about. As the boat's' fore and aft attitude (pitch and yaw - power up and power down) constantly changes, the angle of the fixed transducer is constantly changing at the same rate and angle. By taking advantage of the naturally elevating displaced water, a unique high speed corrective sounding advantage is employed by "placing" the transducer further aftward and upward, allowing it to skim or "surf" as designed by its maker. By doing just this can positivley affect the sounding potential you seek from your transducer.
So, how do we do that?

(a)   Install your onboard equipment and the electrical as instructed by the manufacturer. Leaving your transducer uninstalled (hanging loose). The only item at this point uninstalled to your boat is your imaging transducer.

(b)   Place your boat overboard and move it to shallow water so that your lower unit is well above the bottom. Stop the motor. Do not move the motor from its running trim postion. (This is the postion your motor will be when you arrive at your imaging location).

(c)  Move into the water behind your boat. Move the transducer around on the transom to locations you have previously thought about mounting watching the monitor for best imaging view. Solicit help if necessary to help monitor the screen. (Some become more creative if water isn't their thing, or its just too chilly! 

(d)  Locate the "at-rest" loaded waterline on the transom and mark it. It is generally preferred to install the imaging only transducer above the running surface and below the "at-rest" loaded waterline. This helps with protecting it. We find no advantage by dragging an imaging transducer at speed, so there is no need to install it as though you were going to adjust it for high speed use.    

(e)  When you have located the ideal spot for your transducer mark the location. Tilting the motor to obtain a  desireable "view" is not uncommon.

(f)  Mount with screws or use your SternMate transducer mounting system...move your boat to dry land before drilling, of course.

By following our easy imaging transducer mounting procedure, you can eliminate all guesswork, all unnecessary damage to your boat, having to move your incorrectly installed transducer to some other incorrect location and the aggravation of "wait on hold" when calling in to your marine electronics customer service who suggest you refer to your installation instructions...and you will only get your feet wet once! 

It's a PROBLEM because we create it. Dragging a transducer, forcing it to plow, creates problems (it also creates a rooster-tail), but that's exactly what we are taught to do...exactly like #1 below, or worse. We now know that  there are much more effective methods available to correctly install a transducer. 
[Nature has provided rising water behind the boat all of this time. We didn't realize that this phenomenon will help us gain a corrective advantage when optimizing our transducer sounding. SternMate™ provides the means to help you harness what occurs naturally behind your boat, all in the spirit of avoiding inevitable installation damages. Transducer mounting plates can't do this].
Click image for "stepped"
transom water flow detail
PART 1  -  High speed transducer installation "RULES" 
"Stepped Hull"
Why is high speed transducer sounding optimization such a problem?

*Marine imaging technology is designed for slow, methodical precision use. "High speed imaging", if you were to try it, could be much like driving the freeway searching for the set your wife lost from her ring. In an effort to avoid or out-guess undesireable image interferrence, such as lower units or watercraft architecture prior to the installation of an imaging transducer, it simply is impossible to know what it will  ultimately "see" until after it is installed...or is it?  

What we know...

We also know that "on-board" wiring issues, voltage drops and other settings may be responsible for any transducer sounding problems.

Imaging transducers installed on jackplates or hole-shot are better removed from peril. It also may guarantee an image of the lower unit until raised above its "view". The annoyance of constantly raising and lowering the outboard and overheating an outboard occurs more frequently when intalling an imaging transdcuer on a jackplate. Recent trends are focusing "back to the transom" installation as the most desireable imaging transducer location.

Combination high speed/imaging transducers, when it is desired to use both fucntions, require installation to be followed in Part #1 (above). Many installers will use a separate high speed transducer and will use the combination transducer for imaging only.

"Stepped transom" or "Setback transom"
Follow "RULES" for your transducer installation
​                                                             MORE useful transducer installation information

Prop Wash  -  "Prop wash" NEVER occurs when an I/O or Outboard boat is running at speed. "Prop wash" occurs when reversing or very slow forward, but only when water "boils", or breaks water, into the transom. Inboard boats, at speed, with prop(s) fore of the transom, will thrust or jet water aft into a closely installed transducer...likely affecting a sounding at any speed). When the prop is not breaking water, but simply moving a current of water, that is not prop wash and generally will not affect a sounding.

Twin Outboard or I/O Transducer Installation  -  Install your transducer between the two drives, port or starboard of the drives should there be room, but do not violate the RULES

Transducer Distance between keel or chine  -  Your high speed transducer, when using the SternMate™ system, is best located (with exceptions) from the keel to no greater than 70% outboard (either port or starboard) of the keel. While making a steep bank, generally will cause the transducer to lose contact with the water. Any distance between the keel and 50% of the distance outboard is preferred. 

Port or Starboard Transducer Installation  -  Installing your high speed transducer either port or starboard (or anywhere in (includes imaging X'ducers too) between) is perfectly acceptable. We've heard all the tales about "prop wash" and 
prop rotation affecting a transducer sounding, and it will as long as you are reversing with an I/O or Outboard or moving forward at a very low speed. At speed, water from these outdrive props is jetted aft, not forward...not left or right nor port or starboard (see prop twist). 

Prop Twist (prop rotation)  -  This refers to clockwise (right hand) or counter clockwise (left hand) prop rotation. I/O or O/B prop roation creates an up-thrust of water or a down-thrust of water and has no affect on a high speed transducer when running at speed. All water is jetted aft of the transom where your transducer is installed.

Old 15" Clearance Rules  -   15" rules came about many years ago when external transducers were 1st installed on inboard  boats. 15" was simply a "barometer" used then (and now) to install a transducer aside 15" from the outside diameter of an inboard prop in an effort to avoid interference from the aftward thrust of water.

Current 15" Rules  -  You may see 15" referred to often in transducer installation instructions. When installing a high speed transducer by conventional methods problems are inevitable. What are they? A trailing transducer, when it plows through the water parting it, is certain to generate one of a multitude of problems when the transducer is installed inside of the suggested 15":  (1) Cavitation: potentially this can create burned  areas on a prop blade  (2) Ventilation: a transducer dragging or plowing anywhere below the  running surface of a boat will "part" the water, just as a  plowed furrow a farmer makes in a field. Not only can this disturbed "parted" volume of water (which, otherwise is necessary for adequate prop "bite"), but can cause over-reving and is likely to starve the flow of water to the water pick-up intakes causing engine damage by overheating. Discover Your SternMate™ Transducer Mounting System!
​Let's face it, transducer installation is a critical step when ensuring that your favorite marine electronics perform at optimum. It's daunting, it's damaging, it's misunderstood, and we'll show you how to do it correctly. Transducer mounting problems can be expected with typical "out-of-the-box" and "professionally-made" transducer installations. Once the holes are drilled and transducer is installed, it isn't until then the problems will surface. Sometimes we follow the manufacturers' transducer installation procedures and sometimes we revert to "boating and fishing forum "pros" well-intended advice. So let's avoid the problems and the damages associated with external transducer installations. The "old way" is simply obsolete, so why fight it? It is no secret that when you have the right tools and the correct advice confidence soars and the results are evident.  When you follow the "RULES", you'll know what to avoid and just where to install the transducer(s) on your boat, regardless the make, model, age or horsepower. Call our office...we'll help you.
Illustration Photo (expandable) Reference Help Section
 Video Clip
"Smooth, turbulent-free water" 
Pictorial Illustrations (click to expand)
#1 - Transducer Out of Your Control
#2 - Transducer Under Your Control
​Rule #1  -  Read and understand your boat warranty Exclusions and Limitations (regardless the age of your boat).Read and understand the transducer installation disclaimers provided to you by the transducer manufacturer. Onboard electrical wiring must be made according to the direction of the mfgr. of your transducer.

Rule #2  -  *Smooth, bubble-free, "unturbulated water" does not exist behind any fast moving boat. DO NOT LOOK FOR IT...it isn't there! 

Rule #3  -  Your transducer must "skim or surf" (not plow) and must be in direct, unobstructed contact with the water to obtain an optimum sounding. That's just the way they are designed.

Rule #4  -  Avoid installing your high speed transducer directly aft of a *running strake. Install 2"+ aside.

Rule #5  -  Avoid installation of your high speed transducer directly aft of a *lifting strake. Install at or beyond the "fair" side only, or 2+ from the broad side

Rule #6  -  Avoid installation of your high speed transducer directly aft of a *through-hull fitting. Exception: when fitting is at least 4+ ft fore of the transducer.

Rule #7  -  Avoid installation of your high speed transducer immediately aft of a step designed into a hull. Note: when a 
true step is no further aft than midway of your hull, a transom transducer is a viable option. Do not confuse an architecturally designed stepped hull with a vented hull or a "stepped (set-back) transom". Your transducer(s) can be installed on many "stepped-transom" hulls using SternMate™ equipment. 

When installing a "multi-use" high speed/imaging transducer (when the intended use is dual purpose), install it following the high speed transducer RULES.  See More Useful Transducer Installation Information below
High speed transducers require correct location and correct placement
Copyright © 2008 -2013 Nanticoke Maritime LLC  All rghts reserved
Following C Marine Industries
SternMate™ transducer mounting system can easily be installed on most all boats. Some of the types of boats that use transom-mounted transducers for fish-finders, depth-finders, sonar and fish locators are:

How  to mount a transducer on: All-Purpose Fishing Boats    Aluminum Fishing Boats    Fish and Ski   Bass Boats    Bowriders    Flat Boats    Bass boats    Center Console  Closed Bow Runabouts  Welded Boats   Center Console   Closed Bow Runabouts    Center Console    Closed Bow Runabouts    Cuddy Cabins    Deck Boats    Houseboats     Dinghies   Electric Boats    Multi-Hull Power Boats    Catamarans    Jet Boats   Performance Boats    Pontoon Boats    Stern Drive boats    Cruisers    Skiffs    I/O Inboard-Outboard Walkaround boats   Sailboats    Runabouts    Outboard boats    Electric boats    Row boats    Fishing boats     Fiberglass boats  Steel boats  Painted Wood boats   
Marine electronics manufacturers of fish-finder, transducers, depth-finder, sonar and fish locator, transducer mount equipment:​
EAGLE    Furuno    Garmin    Humminbird   Lowrance    Norcross Marine  Northstar TechnologiesSI-TEX    Raymarine    SIMRAD    Northstar    Tacktick    Uniden    Navionics    Standard Horizon   ​
Disclaimer: The aformentioned marine electronics manufacturers do not endorse SternMate products. 
P: (214) 295-5733
E: nanticokemaritime@sternmate.com
Nanticoke Maritime LLC
Skiff "runniing strake" illustration
"Lifting strake" 
"Running Strake"
​There is a much more to installing a transducer correctly than you may realize