I have an Icom VHF that was hooked up reverse polarity on 12v.

Check your wiring , you may have reversed the power suply with the stan by wires. They are both same polarity, hoever the power goes to fuse and control panel and the standby gos to baterie.

Try Ebay as a source. I have had good luck finding such accessories for reasonable.

Quite a few things can go wrong in this situation. There is an internal fuse that can blow, but the first problem will be a rather large diode that is directly across the DC power input. Reverse polarity will cause this to short, and it usually stays shorted. It will need to be replaced. Then, you should look for open traces from the +12V line to the fuse holder, and the collector of the HF output transistor. If you do not see close to ZERO ohms when your leads are attached, then you have a trace blown off the board.

Depending on how long you left the reversed power on, and if you replaced the inline fuses with a larger value, repair cost can run you from $2 to several hundred, just for the parts! I would take it to someone that knows how to work on this radio. It is not an easy radio to work on.

Contact the Icom service center. Their main web-page is www.icom.com. From there you can select your geographic area and service (commercial, marine, amateur, etc).

Contact ICOM service at www.icom.com, or take it to a marine radio service center.

Probably not the squelch but the speaker on the VHF. These radios are famous for crapping out when getting wet.
Try listening to the weather radio VHF ch 01, 02, or 03. depending on your location and play with squelch.. Keep in mind they do make external speakers you can hook up.

I connected my ICom using the NMEA in. I had the leads reversed first time, moved them around and worked. This was a connection from Furono to iCom but should be much the same

Blue: Speaker (+)
Gray: Speaker ( -)
Yellow: NMEA IN (+)
Green: NMEA IN (- )

Check the wiring again. Installing my M422 needed to switch the polarity of the NEMA input from my GPS75. May be similar problem

Sound like you have an antenna issue. Try a different antenna with coax. If the problem is still there, than you have a problem with the radio. Icom makes really good marine radios but you could have a defective one.