Clarion Radio Replacement 2000 420AC - Where to start?

[EKM]

So I have the original Clarion radio w remote installed in my 2000 420 aft cabin. Radio still works but time for an upgrade. the boat has a Clarion Amp 4/3/2 channel model APA4203 which I assume still works as my base speaker still works. So old radio is pulled out with wire/plugs going to multiple places. What I can see is the plug with the power is pretty much just power with tons of extra wires not used. One plug for the remote (going to abandon in place). So this leave me with a 12 pin plug which I assume goes to the AMP. I tried to trace the wire but could not see how they get to the amp.

So how do I connect the speakers? Do I cut into the 16 wire plug or try to go the rca connectors on the amp? Wiring diagram of the new radio is attached along with pics of the wires in question. The plug with the power only has two wires connected. The radio has two RCA connectors that I don't know where they go to...IMG7406. 7410 has 4 RCA plugs into the amp but it connects to only 2 RCA plugs. 7412 has the has the connections to my speakers (assuming). 7414 is the diagram for the new Clarion Radio (M508 is the model number).

Hoping to get some advice on how to complete the install. Thanks for looking and advice.

 

[Golfman25]

So mine is connected two ways. The RCA plugs go to the amp and power the cockpit speakers and sub. The regular speaker wires go to the cabin speakers.

 

[bahamabreisus]

You might start with upgrading amp and speakers only. Amps can make a huge difference, and of course quality speakers go a long way also. The Clarion head is a pretty good unit.

 

[EKM]

This boat has two clarions...inside cabin has a unit....no amp. And helm unit has the amp. When talking to Crutchfield, they said use the existing clarion amp. The 4 speakers and subwoofer are new. So hoping to go that direction. So much for plug and play. Give me a diesel engine to work on instead. Or AC system or anything but this.