In the boat I purchased this summer, the old cassette player (yes, you read it right) ate cassettes like I eat bacon and couldn’t have tuned in a station on the front platform of the boat.
I was given a gift of an in-dash CD player and marine radio. It was a really great purchase at Amazon with good reviews.
Recently, I tried to install the Pyle PLMRKIT106 marine CD player. I had followed the wiring diagrams to the letter. The wiring harness had four wires: red (live), black (ground), blue (power antenna), and yellow (preset memory, direct to battery). Believing that the only two I needed were red and black I wired in, I attached the ties and couldn’t make the player work. Further believing that my wiring was amiss, I directly attached the red and black leads to the battery terminals, themselves. Again, no go.
Unbeknownst to me, I was moved to tie in the yellow (always powered) lead to the battery. Eureka! It worked. Radio stations were crystal clear. I haven’t tried any CDs yet.
Moral: you must wire that yellow (preset memory) line in to make the player have power.