Will SternMate™ fit my boat? 

SternMate™ will fit on most transoms as long as there is room for the Mounting Plate foot print. 


I have purchased a new fish locator depth finder with color monitor and transom-mounted transducer. The mounting instructions for the transducer advise that upon putting the boat into the water after installation, I should “immediately” check for leaks and any air  bubbles that might be seen coming from the transducer mounting bracket screw holes.

We have read that too! (We have also read the installation disclaimers contained within the user and installation manuals written by manufacturers). That is a valid and substantiated request that they make following all transducer screw-secured installations. You appear to be concerned about  the potential for leaks and so is the manufacturer of your equipment. Should you choose to mount your equipment directly to the transom as instructed, and at first it  appears there are no leaks, you probably won't know for some time whether leaks have occurred or not. By then, water has had time to intrude…how much and how much damage is anyone’s guess. 

Drilling Screw-holes in Your Boat Hull....Could That Be Good Advice?

I have a new boat and will mount my transducer on the transom. I have asked around and some have told me not to worry about drilling holes in my boat  as they do it all the time.  They tell me  that the holes are sealed. Some have told me to screw on a piece of cutting board from "Wally-world" and mount my transducer to that, seal the screw threads and not to worry about it.  They can do that to theirs, but that sort of advice sounds malicious to me!

Oh, we're familiar with most all of the methods and advice given used to attach a transducer to a boat,  thus one of the reasons SternMate was built. They may have taken the advice from  others or maybe they failed to think about the consequences.  Maybe they had no other options at the time or they were just in a hurry, or did not realize the damages that could be created. Should you feel they have provided sound advice, then it is certainly an option.  Most conscientious boat owners;  however, would question it just as you have. Having a choice now to mount your transducer correctly makes it mighty nice and can be a far-cry less costly by doing so. There simply is no shortcut unless you're willing to assume the risk. Most likely the manufacturer of your boat recommends that you refrain from drilling holes in your boat hull...particularly below the waterline. He probably makes that point very clear in your boat warranty.

Screw-holes Are Damaging...Sooner or Later They Will Leak

Will mounting a transducer directly to my transom cause my boat to leak and possibly sink?

Sink?  Most likely  that won't happen since you've probably sealed your screw holes well. What you must remember; however, is that there is the likelihood at some point that any screw-hole below the waterline or anywhere else for that matter which water can access, could leak. Water will, when given an opportunity and when you least expect it,  intrude and most always causes damage. How long it takes before you realize it is unknown. FACT: The "at speed" tugging and snatching by water dynamics against a transducer will loosen and compromise mechanical thread-fastening grip inviting boat leaks regardless of the use of your favorite sealants.

Boat Warranty...For the Life of Your Boat

My boat is out of warranty and older. Why would I be concerned now about drilling holes below the waterline?

We'd think you would want to continue to take proper care of your boat regardless of its age. An older boat is just as susceptible to leaking as a new one. The manufacturer of your boat most likely had the  "modification and alteration" language in your original boat warranty. We would recommend to take heed as if it could have been a problem when the boat was new, it could be a problem even though your boat is older now. In short, the manufacturer simply did not care to pay for a  claim from leaks or damages from alterations or added equipment after it was built. Its a good policy to follow for the life of the boat. Does drilling holes in a boat below the waterline really make sense?  

                Aluminum Boat Patch...Refit with SternMate™

We are often asked how best to repair or fill transducer mounting holes drilled in aluminum boat hulls. Most of the questions come from those who are changing transducers and now have extra holes because their new brackets do not line up with the old.  Some just cannot stop the small, irritating leaks from their existing  transducer mounts.  Fortunately, there are some excellent sealants to plug up those holes, but most object to that sort of unsightly repair.  Some have had aluminum plate welded over the holes, painted to match the boat, but that could be quite expensive and you'll end up with an obvious unsightly patch. Sometimes the holes are brazed or filled with weld, ground off  smooth, the boat having to be repainted to match.  Welding in an aluminum patch could very well cause even more problems. Heat from the weld will most likley be too great and create unsightly warpage in  the aluminum skin of  of your boat hull.

The simplest, quickest and most effective way to remedy leaking  or "extra" transducer mount screw-holes in aluminum hulls is with SternMate. The screw-holes should be filled with a product such as Marine Tex,  "JB WELD" or PC 7" and flush sanded smooth. SternMate can be installed directly over your repairs and we find that most make no repairs and simply install SternMate™ directly over the screw holes....pretty slick, huh?

SternMate™ Makes Transducer Installation Easy

Is SternMate difficult to install?                         

No, not at all! Installation instructions are illustrated and  detailed, but the process is simple. The instructions are furnished in the kit and must be closely followed for a proper installation.  Ask your dealer  to install it for you if you wish. 

Chipped Gel Coat During Transducer Installation

I installed a transom-mounted transducer last summer on my fiberglass boat. As I began to drill, I knocked a piece of gel-coat off with the drill bit nearly the size of my thumbnail. It looks awful. It makes me ill every time I see my boat.  Should I have it repaired and reinstall with a SternMate? I am so disappointed I had not found SternMate sooner.

Unfortunately that happens more often than not.  Pride in ownership of a nice boat would cause most proud boat owners to have the damage repaired and reinstalled with SternMate. You’ll be much happier.

Transducer Adhesives..."let's glue", not screw it ...(up)!

I would like to use an adhesive to attach my transducer to my boat hull so that I do not have to drill holes. I am concerned that store-bought adhesive may not be strong enough  and might not hold.

It's a great idea to attach your transducer without drilling screw-holes; however, it might be very difficult to locate an "off the shelf" adhesive to perform satisfactorily for that application. The design of SternMate™ is closely calculated to assure the perfect "marriage" of extreme demand adhesives-to- materials bonding strength specifically formulated for the installation of  SternMate™ to a fiberglass, aluminum, steel or painted wood boat hull following our simple preparation instructions. 

Retrofit an Older Screwed-to-the-boat transducer...Eliminate Old Problems

I have a transom transducer on my boat now. Can I replace it and mount it on SternMate?

Yes. SternMate is perfect for a re-fit. As long as your gel-coat is firm and intact and you may choose to fill the old screw holes, or not. SternMate™ will install over the old holes and you’re in great shape for a re-fit.  In fact, this question has come up many times as boat-owners are keeping their boats longer and are more conscientious about maintaining them. Note: Do not abrade away the gelcoat surface. Unless you will be mounting your transducer in an entirely different location, install SternMate directly over your repairs in the event you make them.

Water Dynamics Takes its Toll on Your Transom-mounted Transducer

I am getting ready to install a transducer on the transom of my new $30,000 fiberglass bass boat, but it makes me nervous to drill. Do you recommend a sealant?

Anticipation like yours is normal. There are many reputable sealants and they might seal your screw-holes...and they might not.  Drilling and  then hoping that your screw- holes are sealed is not required to  mount your new SternMate. You will find that adjustments will always have  to be made to your transducer once you install it. Each time you  make an adjustment 
you will have to break the screw seal,  reseal the screws, and most likely weaken the integrity of the screw-hole by stripping out the threads in the delicate fiberglass.  The dynamics of water tugging against your transducer as your boat moves through the water can be significant. This action can compromise the grip of the mounting screws, the sealant and the integrity of the installation. SternMate is designed to eliminate all of that anxiety. I’d be mighty nervous too!

                  SternMate™...for an Optimum Sounding

                 I have a sonar fish locator on my boat which has a transom transducer. The provided transducer bracket has limited adjustment capability and I am unable to get a decent reading much faster than trolling speed. It has become quite frustrating.  

There could be a number of causes, such as improper wiring, wire guage and run, voltage drop upon acceleration, interfering obstructions, (I.e. lifting or running strakes or thru-hull fittings fore of your transducer). Water is a mess back there and SternMate™ helps you in a very uniuqe way to adjust it correctly. By installing SternMate, your transducer is moved aft and adjusted upward, oftentimes above the running surface of your boat. Contrary to popular transducer mounting instructions, we do it differently because it makes sense and works. Unfortunately, fine-tuning  any transducer to operate at its optimum involves trial and error. SternMate is designed to make that task so much more pleasurable. A retro-fit with SternMate could very well be the answer. You may have to fill holes and remount your equipment. Check well for evidence of water leakage from the screw holes in your boat before filling.

There Could be Water in Your Boat Hull

I recently removed my older transducer and noticed a trickle of water coming from the screw-hole.  I did not particularly like what I saw, but installed my new transducer and sealed up all the holes. I'm wondering if there is more water in my boat than I realize.

The water in your hull may not be intruding at your transducer screw-holes, but elsewhere. Fiberglass wicks water like a sponge  through capillaries and voids in the composite and oftentimes your boat will get heavy. If you notice a performance loss, it may not be your motor, but your boat. Foam soaked flotation can become very heavy and, unfortunately, waterlogged foam will not dry out. We have addressed elsewhere in this section frozen water and the damages it can cause. When water is wicked into the fiberglass and freezes, it will expand causing delamination and more room for more water to enter. The cycle continues absorption, freeze, expansion and can ruin a boat. Aggravating the situation by drilling holes is not recommended. Water contained in a boat hull simply never goes away.

SternMate™... It's Like a Jackplate for Your Transducer

SternMate is such a well planned idea for a transducer. I have mounted my outboard on a jackplate so that I can gain maximum performance of my boat.  SternMate apparently  follows a similar philosophy...a transducer on a jackplate...what a cool idea!

Thanks! SternMate was designed around that concept, not only with optimum transducer sounding performance in mind, but having  eliminated the necessity of screw-holes below the waterline. We have found that  many have not considered the consequences and frustrations associated with mounting transom- type transducers. The jackplate idea has been around for a long time...a boat racer's best kept secret until the early 70's. It is primarly used to gain maximum performance of your outboard boat.  We are the first ever to have used the concept for a transducer. So, you are correct. It actually is a mini jackplate for transducers.

SternMate™ Installs Easily on Aluminum Boat Hulls

My boat is a painted aluminum. Will SternMate install on my boat?

Yes. Follow the simple instructions as you would for mounting SternMate any other boat;  however, the paint must be gently removed to the bare aluminum (see instructions).

SternMate™....Installation in Underwater Applications

I am interested in installing new electronics on the transom of my my boat which is currently docked.  Can SternMate™ be installed underwater without having to haul my boat out?

Yes! SternMate™ can be installed under water.  SternMate™  adhesive is suited for underwater installation.

SternMate™...A Sound Investment for Your Boat

I have drilled holes in my boat many times and have not experienced leaks. Why should I invest in a SternMate?                        

So have we! We have heard that comment many times. Some folks don't care and for many there have been costly consequences. There is a high probability that the leaks you  "have never experienced" have yet to be noticed. Why take a chance like that when now you don’t have to? Think of SternMate as a great way to ensure it " won’t happen to you".  Slow water intrusion into a hull can go undetected for a long time and, you know as well as we do, that water can cause all sorts of damage....and never dries up. Consider this:  Someday you may decide to sell your boat which has equipment that you have attached, or possibly even your dealer had installed for you,  with screws below the waterline....a transducer in this instance. You could very easily eliminate the savvy boat shoppers in the event that he or she were to make a water intrusion examination of  your boat simply by removing a couple of the transducer mounting screws....and water dribble out.  Just how would you explain that or convince anyone else for that matter, that your LEAKY  "TIKI" was "retaining" water through no fault of your own?

Forum Quote from a DIY Transducer Installer  9/5/2010

"Installed my [transducer] tonight. Easy install and so far the unit seems good will find out tomorrow when she hits the water. I did break a dang screw off in my hull. So now I have to repair my boat that has 5 hours on it. Oh well crap happens".

Wonder if the repair job will be as nice as the installation?

Transducer Mounting Questions, Concerns, Comments - FAQ
​This website will teach you everything you might not know about HOW and WHERE to correctly mount your transom-mounted transducers. 
Something to Ponder...
If water can leak into screw-holes, it is most certain to leak out of screw-holes...particularly during a water intrusion boat warranty inspection.
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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:

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 Technologies SI-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

Boat owners ask about installing Transducers