I have a jbl marine stereo that power button works but when you press the mode button nothing happens. I f you hold the mode button in the FM works but as soon as you release the button the FM goes off

Question edited for clarity, proper 'make model (what it is)'.

I can't find a manual, but they have a common theme. Remove the faceplate and press the Reset Button, then clean the contacts both sides with electrical switch cleaner or Isopropyl Alcohol.

https://www.premiumleisure.com/Manuals/nov07/Hydro_Spa_JBL_Stereo.pdf

https://www.rocktheboatmarinestereo.com/specs/MR18.pdf

https://www.google.com/search?q=JBL+marine+MR-15b+manual

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Try doing default factory settings.
Step 1. Press the "Power" button located on the top center part of your JBL Charge 4 Bluetooth speaker. The speaker will be powered on when the LED backlight under the Power button is lit.
Step 2. Hold down the "Bluetooth" and "Volume Up" buttons at the same time for roughly three seconds. The Volume Up button looks like a plus sign. Additionally, it's important to hold down the "Bluetooth" button in the center of the device next to the Power button, as it's easier to hold down. After three seconds, the LED ring around the Power and Bluetooth buttons will briefly light up before the JBL Charge 4 powers down.
Step 3. Press the "Power" button again to turn the JBL Charge 4 Bluetooth speaker back on. The Charge 4 will instantly turn on in Discovery mode, with the Bluetooth LED blinking on and off, and the speaker making a pinging sound. This confirms that you've successfully reset your JBL Charge 4 to its default factory settings. You'll need to pair or re-pair any devices you want to play audio through the JBL Charge 4 speakers with the device.

before you press the cd on button keep holding the eject button while you press power on, I know this works for computers etc.

I have the same model stereo in a brand new hot tub that was having the same issue. To fix it all u need to do is pull the front cover off to access the pump controls and in there you will find a black box where a power cable runs yo the stereo. There are two screws that open a little door in the black box. In there you will need a small flat head screwdriver to move a redswit over to the 110 volts position. Turn the radio on and it should work. That black box just controls the power to the stereo.

JBL is at best a low quality marine grade brand of stereo. It is now garbage. I have worked on hot tub stereos for many years, PolyPlannar is the only one that is any good. If it was bought 30 days ago, where's your warranty?

You will find the maual you need by using the following link :

http://www.prospecelectronics.com/JBL%20MR6%20manual.pdf

yes i am a repair shop and i have had nothing but problems out of those units you might want to look into a different unit boss marine is a good choice

To get your Sirius ID number from you MR-17 JBL stereo, select the Mode button until it displays "Sirius". Then push and hold the Mode button for a couple seconds and it will chirp and display 3 blank spaces. Enter three zeros, "000" in these 3 spaces. The Zero is the loud button labeled "LD". When you do that, it will display your Sirius ID number. :)

yes you can hook up your mp3 to an aux input on a stereo not sure what you mean by converter typically it is done through a 3.5mm - 3.5mm standard audio cable. and in order to do this your reciever must have an aux input of course and if so then you can toggle the mode of input by pressing the Mode or button that switches from radio to cd etc or consult with your users manual to find out how to switch and if aux input method is supported

this normally happens with a lot of sets! It usually happens during a Power Failure, Power Surge (Fluctuation) and if the wire of the component is taken out from the wall outlet while the system is on...To get rid of this problem all you need to do is to press the Display button on the main unit, it is located just below the main display! Voltage Selection has got nothing to do with this problem...