1990 MONTAUK 17: Thru-hull SONAR Transducer
1990 MONTAUK 17: Thru-hull SONAR Transducer
I'm considering installing a depth transducer in the bilge of my 1990 Montauk. Has anyone else done that? I have a Raymarine MFD which uses a 2-inch-diameter low-profile through-hull transducer. What is the hull thickness if I were to cut a 2-inch-diamter hole? Trying to make sure the transducer has enough thread to be properly mounted. Any info appreciated.
Re: 1990 MONTAUK 17: Thru-hull SONAR Transducer
I am not clear on where in the double-bottom hull you plan to install the SONAR transducer on the MONTAUK 17 boat. You mention "the bilge," but a Boston Whaler MONTAUK 17 hull does not have any bilge space. The hull is a double bottom hull and the interior is filled with foam. There is no bilge.
If you are planning to install the SONAR transducer in the cockpit sump, you can probably get a good appreciation of the thickess of the double-bottom there by using the existing through-hull drain in the sump area as a guide.
Usually on Boston Whaler boats, due to the double-bottom constructions and foam-filled interior space, use of a through-hull transducer is not practical except on boats where the design of the hull has provided a special area for installing just such a device. This area is called a putty box, which means that the space between the double bottom hull in that location has been filled with a setting putting instead of with foam. When a large-diameter hole is drilled through the putty box, the putty gives the area reinforcement, and it also helps to make a shield to keep water from migrating into the foam.
As a general rule with boats that are kept on trailers, installation of through-hull SONAR transducers is a problem due the potential for keel rollers or support bunks to contact the transducer. The generally rounded center hull portion of a MONTAUK is also a problem, as some sort of fairing block would probably be necessary to get a good fit for the transducer body against the curved hull surface.
Also, I would be very surprised to learn that a modern SONAR could only use a through-hull transducer. Most every SONAR that is appropriate in size and cost for use on a small boat can work with a transom-mount transducer.
If you are planning to install the SONAR transducer in the cockpit sump, you can probably get a good appreciation of the thickess of the double-bottom there by using the existing through-hull drain in the sump area as a guide.
Usually on Boston Whaler boats, due to the double-bottom constructions and foam-filled interior space, use of a through-hull transducer is not practical except on boats where the design of the hull has provided a special area for installing just such a device. This area is called a putty box, which means that the space between the double bottom hull in that location has been filled with a setting putting instead of with foam. When a large-diameter hole is drilled through the putty box, the putty gives the area reinforcement, and it also helps to make a shield to keep water from migrating into the foam.
As a general rule with boats that are kept on trailers, installation of through-hull SONAR transducers is a problem due the potential for keel rollers or support bunks to contact the transducer. The generally rounded center hull portion of a MONTAUK is also a problem, as some sort of fairing block would probably be necessary to get a good fit for the transducer body against the curved hull surface.
Also, I would be very surprised to learn that a modern SONAR could only use a through-hull transducer. Most every SONAR that is appropriate in size and cost for use on a small boat can work with a transom-mount transducer.
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russellbailey
- Posts: 99
- Joined: Tue Nov 03, 2015 11:03 am
Re: 1990 MONTAUK 17: Thru-hull SONAR Transducer
I did similar in my 1984 Outrage 25. I meant to send pictures to jimh of the install but could not locate them.
It is not hard but does take some fiberglass work. I have an Airmar tilted element transducer, installed through my fishbox. At this location, the foam part of the hull is about 4-5" thick.
Follow the Airmar instructions for a cored hull, but this "core" is deeper than their instructions. You end up making a 0.5" or so thick epoxy cylinder that seals off the foam core. The inside diameter of the epoxy cylinder is essentially the same as the transducer hole through the hull. Managing heat as the epoxy cures is important, and the epoxy cylinder will likely have to be recessed below the inside hull surface - in my case I had to do a two stage cylinder - the standard one as in the Airmar instructions, and then a larger one to allow the transducer nut to engage the threads.
It was nervewracking drilling the hull through the boat but the overall project was not difficult and gives great results.
It is not hard but does take some fiberglass work. I have an Airmar tilted element transducer, installed through my fishbox. At this location, the foam part of the hull is about 4-5" thick.
Follow the Airmar instructions for a cored hull, but this "core" is deeper than their instructions. You end up making a 0.5" or so thick epoxy cylinder that seals off the foam core. The inside diameter of the epoxy cylinder is essentially the same as the transducer hole through the hull. Managing heat as the epoxy cures is important, and the epoxy cylinder will likely have to be recessed below the inside hull surface - in my case I had to do a two stage cylinder - the standard one as in the Airmar instructions, and then a larger one to allow the transducer nut to engage the threads.
It was nervewracking drilling the hull through the boat but the overall project was not difficult and gives great results.
Re: 1990 MONTAUK 17: Thru-hull SONAR Transducer
I would NOT do it.
Cutting or drilling into the hull increases the chances of water getting into the hull. It is a discouraged practice. Only the large boats (22' of larger) had a special fairing block for thru hull transducers.
Russ's boat has a completely different layout and the hull is significantly thicker than the Montauk 17.
The Montauk bilge is small and barely contains a bilge pump and the the thru hull rear drain.
Mount the depth sounder on the outside of the transom. It worked on my 1987 Montauk without significant cost or effort.
Cutting or drilling into the hull increases the chances of water getting into the hull. It is a discouraged practice. Only the large boats (22' of larger) had a special fairing block for thru hull transducers.
Russ's boat has a completely different layout and the hull is significantly thicker than the Montauk 17.
The Montauk bilge is small and barely contains a bilge pump and the the thru hull rear drain.
Mount the depth sounder on the outside of the transom. It worked on my 1987 Montauk without significant cost or effort.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003
Re: 1990 MONTAUK 17: Thru-hull SONAR Transducer
All, thanks for the thoughts on this. I was considering a depth transducer that required a 2" hole cut. Was looking for an alternative to a transom mount since we tow skiers and also didnt want the extra wires over the transom and exposed hardware. Would have been just in front of the bilge pump in the bilge tunnel. Was going to do a thorough bedding with 5200 to seal it and eliminate the risk of water intrusion into the hull foam. But, Phil, I think you are correct, its too much of a potential compromise of the hull integrity. Thanks for the help.