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Challenger 180 - Custom Brackets for 6.5” Speakers

CrankyGypsy

Jetboaters Captain
Messages
352
Reaction score
296
Points
202
Location
Tampa, FL 33615
Boat Make
SeaDoo
Year
2008
Boat Model
Challenger
Boat Length
18
(referencing a 2008 Sea-Doo Challenger 180 non-SE)

The stock hole seems oversized even for the original 7” speakers. The previous owner installed a pair of marine Kenwood 6.5” and had to place them in there off-center, with only three screws. I was not going to let my replacements be held this flimsily, so I came up with a solution to securely mount the more common 6.5” size and keep it looking factory.

Supplies:
White HDPE that is 3/16” x 12” x 24”
6.5” Marine Speakers with Hardware (I used a pair of Polk’s db651)
The original speaker screws (or equivalent)
Washers that fit the old speaker screws (likely will need eight)
A couple very small coarse-thread screws (for wood)
Long M6* screw with washers and nuts (your bolt size may differ - read below)
(only use stainless steel hardware for anything staying on the boat)

Tools:
Power Drill and bits
Jigsaw with 18tpi Metal Blade
Dremel with cutting disc
5” Hole Saw (or whatever the speaker requires for mounting)
3” to 4” Hole Saw (not required)
C-clamp(s)
Philips Screwdrivers (one regular and one stubby)
Sharpie
Drafting Compass and cardboard
Sanding Block with 40-80grit
Drill Press (not required, but helpful)
Deburring Tool (not required, but useful for quick, smooth edges on the HDPE)

I made a cardboard pattern with a compass that was just over 7” in diameter. I transferred this onto the corner of the HDPE with a Sharpie then drilled a pilot hole at the center. I used a 4” hole saw to cut the center and then the jigsaw to cut the outer perimeter (you can use the jigsaw to cut both). I will refer to this bracket as “the donut.” Clean the edges up with sandpaper or the deburring tool after every cut.

With the speakers out, I removed the rear seats and then removed the storage units underneath to expose the engine and fuel tank area. This allowed me to pass the 7” donut around and behind the original speaker hole. On my Challenger, the fiberglass on the backside of this area was not level. I had to cut a chunk from the outer edge of one donut and then shave an edge down on the other to get the brackets to sit flush against the back of the original speaker hole. It took a few trials of cutting/grinding and fit-testing until I was satisfied ...don’t rush it by removing too much at once or moving on without getting a nice, flush fitment. Be mindful of the original four screw holes, as you want to make sure you have enough material here to secure the donut at these points.

01.jpg

Use a C-clamp to secure the donut behind the original speaker hole - it doesn’t have to be exactly centered, it just needs enough material around all four screw holes for mounting. It may be helpful to mark the donut “Up” with the Sharpie. Find a drill bit that is only slightly smaller than the original screw holes and transfer these holes through to the donut with the drill. Remove the HDPE and enlarge the donut’s transferred holes so the original screws' threads will fit through easily.

Take the original speaker screws and add a washer to each. Place the donut behind the speaker hole again and screw the original screws in from the backside of the donut. I did this a few steps later, but you can now use the Dremel to cut the pointy tips of the screws off so they are flush with the gelcoat. I found that I had to retighten the screws after cutting and had to grind them a little more until flush.

02.jpg

The original speaker hole is about 6” in diameter. We need to make another HDPE disc that is as close to this as possible without being too tight. I found the best method for this was to use a compass to make another pattern for an HDPE disc that is a fraction larger, drilling the center with a small pilot drill, and cutting out the perimeter with the jigsaw. Then, using the same sized center drill as the hole saw, I enlarged the pilot hole. *For my Milwaukee Dozer hole saw, this allowed me to slip a long M6 bolt with a fender washer through the center. I secured this on the other side with a second washer, a lock washer, and two nuts. I then placed this in my drill press set at the highest speed. With a sanding block of 80grit, I “turned” the disc down little by little. I took my time checking fitment and then returning to the press until I had the disc turned down so that it filled the original speaker hole without being forced. You may be able to accomplish the same using a hand drill and a sheet of 40-80grit secured to a flat surface.

03.jpg

To drill the center of the new disc out for the 6.5” speaker and also have it match the donut, I placed the disc in the speaker hole, and marked the orientation with the Sharpie (note the line in the next pic at about 12 o'clock). Near the edge, at about 3 and 9 o’clock, I marked and drilled two small holes for a couple of tiny wood screws. With the newer disc now secured to the donut, I used the 5” hole saw to make the recess for the new 6.5” speaker through both layers of HDPE. The tiny wood screws are no longer needed and will likely need to be removed afterwards.

04.jpg 05.jpg 06.jpg

In order to get an accurate placement for the new speaker screws, I tried a few things. The first attempt did not work which was using a piece of aluminum that was C-clamped as a guide - the fact that the screws have to pass along the contact edges of fiberglass and HDPE make it very difficult to keep the drill from pushing this guide where the bit wanted to go (into the softer HDPE). What I found worked really well for me was to use the included speaker bracket that came with my Polk db651 speakers. I centered and C-clamped this bracket onto the outside of the speaker hole, allowing plenty of room away from the old holes. With the drill turning very slowly and applying minimal force, the four screw holes were placed accurately. I turned the screws in to tap the new holes and then removed them for the final install.

07.jpg 08.jpg 09.jpg

Done.
 
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