I don't know anything about for boats. But you could call the city hall or the police dept and ask them. That's what I'd do.
Unfortunately now most of it there on the Port Orchard Waterfront is paid parking although handicap is free I believe for all of it. There may be spots as well but you are correct! There is a marina. It's down around by City Hall I believe. Chamber of commerece is is good resource to call for info. Believe it or not. I was never even aware of its value or presence until my Aunt told me their still around and WHO&WHAT THEY ARE. NOW days they are prob. also online. Check for info there too. Good luck.
The park is daylight use only. The closest camping would be Manchester state park (unless you're boat is large enough to stay overnight at the marina)
The boat launch is around the corner by the bank but no overnight parking
I've never noticed signs that said no parking overnight. Yes there is the marina and a few boat launches, I would just keep an eye out where you park your make sure it has no time limits or towaway signs.
Thanks! Your answer is awaiting moderation.