I wouldn't minding finding a decent built-in FM Radio/MP3 player to
install on Yo Ho if I don't sell her. Any recommendations in the $200 or
so range?

Easily done at that price. In 2004, purchased a used 18 foot Sea Doo jet
boat to futz around with. It had a factory AM/FM/Cassette head unit. I
replaced it with an AM/FM/CD/MP3 player. I think it was an Alpine (sold the
boat in 2005), but it matters not as there are a number of brands of decent
quality similar players out there in that $200-$300 price range. The point
is, the CD player will read CDRs that have MP3s burned on them. I was able
get 150 MP3s to a single CDR. I kept a CD wallet filled with 10 such CDRs
in the glove compartment of the boat. Took up very little storage space,
which is important on a small boat.Those 10 CDRs contained the 1500 songs
that were on my portable MP3 player. What was nice about this solution was
that I didn't have to remember to bring the portable player, and didn't have
to secure the portable from getting knocked around or getting wet. No patch
cords needed. And, if the discs on the boat got stolen or destroyed from
heat, all I was out was $2.50 for the cost of the blank media. I kept
backup copies of the discs at home, just in case I needed to duplicate them.
Pop a single CDR in the player, set it to shuffle play, and it was good for
the day.