Polyethelyene plate 
"eliminates
unnecessary holes" 
 What do the famous boat and equipment manufacturers say about warranties?
 WARRANTY STATMENT LANGUAGE and disclaimers are all generally worded very similar.
"MODIFICATION and ALTERATION"  - "EXCLUSIONS and LIMITATIONS"...it's in there!

Warranties are drafted to protect the mfrg. from you and you from yourself for installation damages created after the boat left the manufacturer.
Highly resistent to adhesives - Polyethlyene cutting boards may not be UV stabilized and quickly deteriorate 

NOTE: "Starboard™" is a high quality, UV stabilized, proprietary polyolefin thermoplastic and does not recommend using adhesives 
only without fasteners when fastening to itself or other substrates."Starboard™" has a very high thermal expansion rate (heat/cold)...it moves alot ...Expands and Shrinks...and can easily separate itself from an type of adhesive bond attempt.

​EXAMPLE: Transducer mounting board glued to a hull which has been sitting in hot sun backed into cool water can easily "fracture" the bond = adhesive failure. How? The transducer mounting board and adhesive shrink and swell at different rates in accordance with temperature and moisture exposure.
Abrading (sanding), undercutting, "dovetailing", thread-cutting simply creates more surface area of the same material
*(provides no advantage for transducer optimization)
"…that water intrusion or associated damages occurred from mounting this type of accessory (transducer), would the Ranger boat warranty accept responsibility and cover repairs or replacement for this type of claim upon determining that leaks actually occurred at the transducer mount screw holes?
Ranger Boats   
From: info@RangerBoats.com 
Sent: Fri 10/30/09 3:57 PM

 "The installation of a transom mounted fishfinder itself would not void the warranty, but any damage deemed to be caused by or resulting from its installation would not be covered under Ranger warranty. Hope this helps. Thanks again and let us know if we can be of further assistance".

Sincerely,
Greg Marler
Ranger Boats
Famous maker Transducer Mfgr. 

[Disclaimer from LEI installation manual]:
“…or for any loss or damage resulting from any other cause whatsoever. We will not under any circumstances be liable to anyone for any special, consequential, incidental, or other indirect damage of any kind".

LEI Extras
PO BOX 129, Catoosa, OK
(Lowrance and Eagle products)
Pub. 988-0147-581 
Carolina Skiff "Modification and Alteration" Warranty Statement and Explanation


Stingray™ Boat Co. 

Warranty Information: (excerpt)

This Warranty does not cover the following:

“(d) Options and accessories installed after the boat was manufactured by STINGRAY, and/or any damage caused thereby:"
Carolina Skiff 
Transducer Mount. "Rooster-tail" containment
How many screw-holes?
An expression of indecision
Clear view 
"rooster-tail" shield. 
Correct spot 
  this time?
You've seen 'em look just like this
Checkmate Power Boats (warranty excerpt)

"This limited warranty does not apply to: damage or effects
of such damage caused by the installation of engines, 
accessories or other equipment installed by anyone other 
than CHECKMATE MARINE, INC."

Triton Boats says:                  December 02, 2009 12:58 PM    To: Captain Chris
Subject: Re: boat warranty

"Captain Chris,  Triton's warranty does
not cover the installation or damage caused by an external transducer mount through our warranty statement.  Only hardware factory installed is covered regarding electronics".

Thank You,
Marty Morris
Transducer installation is justifiably intimidating to many installer/users. 

   Many dealers will not install transom transducers...the liability is simply too great​     
           (Don't forget to ask him for his "stand-alone" transducer installation liability warranty statement)
  • Incorrect multi-attempt installations are common and result in many unnecessary screw-holes and, of course, boat damage
  • Damage is always caused by “mechanical fastener” transom-transducer installations 
  • The installation of “plastic cutting board-type mounts” create a damaging installation
  • Common installations oftentimes create difficult or impossible transducer sounding adjustment capabilities
  • Transducer upgrades almost always require a new set of damaging screw-holes
(click the photos below to enlarge)
2010 Carolina Skiff 
DVL water in hull.
Transducer Photos  -  Transducer Mounting Boards  -  Transducer Mounting Plates  -  Gizmos  - Rig-a-Rounds
This gentleman had an idea.He says, 
"the light went on!"
Transducer Installation FACTS
Read Your Boat Warranty before installing your transducerDamages created after your boat left the  factory, from installation of equipment not installed by them, could likely be damages (leaks, water-soaked flotation) and costly repairs you'll wind  up financing alone.  Insist that your dealer read it also!
PLUMB DANDY
...a toilet flange, of all things!
Eliminates
Screw-holes?
Professionally
installed transducer
Transducer Mounting
Board
​Polyethylene transducer mounting boards - Plastic transducer mounting blocks - Poly plastic cutting boards
         (*Transducer mounting boards are not "Teflon" and they aren't "Nylon"...they are polyethylene and just as "unstickable" as the next)
All sorts of 
anti-spray ingenuity!
It's difficult to believe, that these boat owners ever intended commit these atrocities to their boats, but they have!
Your rooster-tail
containment appartus
here.
A boat with a cutting board for a transducer mounting plate probably has a cinder block in the bow for an anchor
When your dealer offers to install your transom transducer, ask him for his written liability statement. 
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:

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
"...Our factory warranty doesn’t cover any type of modification or alteration, which includes mounting transducers to the transom...

...If water does leak into the screw holes created by himself or another person, this would not be covered by our warranty. Our warranty only covers manufactured defects in our workmanship".

Emily J. Snyder Warranty Department
Carolina Skiff, LLC
Nanticoke Maritime LLC

Transducer Installation Consequences