Wylietunes

So you've eliminated everything upstream of the amp. odds are slim to zero the noise is entering in the speaker wires.

Are they power by their own amp? Technically, this can be one half of a 4 chnl amp thats also powering the main cabin. Do they have their own pre-amp signal supply or is it shared with all the cabin speakers? This starts to isolate the issue.

The 4 full range chnls of the javelin deliver 150W rms x 4 @ 2 ohm, so thats 75W rms to each speaker with a pair in parallel p/chnl. I do not think you have a too much power issue, but maybe a cross-over issue. Id start with tuning.

Are all 4 the same size and type? Are the 2 you want to address, wired together on one channel or are they in parallel with the other pair? What is your goal for the 2?

Diagnose the failed component and order a replacement part. All three audio components are serviceable and usually in stock at the factory.

I guess a transom remote is now an option as well.

I doubt this is a 1 model year and done for JL. Given the time needed for the design team to work out the details, then the retooling needed to start production of new components. New parts, such as the dash panel to house a new media unit, was likely in production long before the actual 2021 model production began. MBs decisions to go a different route, likely began 6-8 months ahead of the new model release. Then theres the negotiations between boat builder and vendor to finalize the build plan. Prior to that is the bidding phase.

Ethanol and octane need to be two separate discussions. What the disclaimer is about, is the fact that ethanol blended fuels have a lower BTU (energy) then their pure gas counterparts. This means a reduction in performance, usually noticed in lower MPG/HPG and is not about octane. For me, running the proper octane, or higher if thats whats available, is most important. Proper octane PLUS no ethanol, is a bonus.

If the batteries are going dead when the boat is not in use, then its likely not how you use the switch while using the boat. However, this does not include putting the boat away with one battery dead because it has loads wired directly to that battery, and the switch was not on that battery or BOTH. I would look to see what loads, other then the auto bilge, are wired direct to a battery, circumventing the switch. Wire through the switch and most likely your dead batteries while on the lift issue, goes away. Even better, swap the 1/2/BOTH/OFF Perko for a OFF/ON/BOTH Blueseas and an ACR. No more monitoring the switch while on the water.

Your 2018 does not have a Sirius/XM compatible media unit. So you would have to go with a universal SAT unit that connects with via a music signal only audio connection, much like a headphone jack.

If this is a new boat, then let the dealer work with MB to resolve. Youve paid for the warranty. If its a used boat thats new to you, first thing is to see if any non OEM installed audio gear, is installed. Where the B+ and B- are terminated, makes a difference. Amp gain can create unwanted noise. Incorrect or cheap RCA cables can lead to noise.

Poor seal at the fake-a-lake or loose hose, etc, causing air leak. Air leak at impeller housing gasket.

Five years ago yeah. But currently, there are marine grade class-D amps delivering that kind of wattage in the price point. That old gen, and even the new gen, 600.2 has an open chassis as its fan cooled. This has humid air flowing across the PCB all the time. This can eventually take its toll on the amp. If you do go with a new tower amp, id consider the re-purposing the existing marine grade Syn-2 bridged to the woofer. Ive done this another of time. Its actually he marinized cousin of the KS300.2. The stock Wet Sounds XS-10FA has an RMS of 300W and a peak of 600W. So it will handle the desired wattage of the amp you have or thinking of going with. Both are 10", so the amount of output will be similar. So no real advantage to the change, unless. The cavity behind the woofer is completely sealed and close to the ideal net internal volume for the 10W3. Would actually be a step back in performance and sound quality, if that cavity is large open to the bowls of the boat, as the XS-10FA is a true infinite-baffle woofer, and designed to have that large, open cavity behind it. The biggest issue I see with those stock woofer setups, is a poor seal between the woofer and deck. This has to be addressed, regardless of woofer. Either way, definitely move the woofer off the existing 6 chnl, freeing up those two chnls for the in-boats, so each has their own chnl. I would also consider trading the 4 rev-8 8" HLCD for a single pair of larger 10" Rev-10 HLCD. For surfing, most do not miss the peak volume of four smaller HLCD, but benefit from the increased mid-bass of the larger driver.

The pic in this post, looks like a binding hinge as the possible root cause. The force is applied by the actuator, and the weld is giving closest to the hinge.

If the amp has a stainless steel shroud, its the Syn-4, 4 chnl. Woofer on one half and 4 main cabins on other amp, bows on head. If its the gray amp with black end caps, its the 4 chnl HT-6. 2 extra chnls for the bow. I cant remember what year the switch was made.