Holding Tank Pump Out

So, my 32-2 has a holding tank with an overboard pump, but no deck fitting for dock pump-out. Seems odd to me, but there are a couple of these oddities in my particular vessel.

I'm wondering how I go about pumping out what I can only assume is a years old seawater-urine mixture in the holding tank currently. Lovely.

Am I to simply open the inspection cap atop the tank and vacuum this s*** out? Pun intended.

I plan to add a proper Y-valve and deck fitting soon(ish), but it's somewhat low on the project list; which keeps growing, as you all can undoubtedly relate to.

Cheers.

Odds are that when the boat was built, and for a decade further on, it got by fine with the original marine head and overboard thru hull.
Someone later copied part of the 80's EY system with a holding tank and a manual pump for valving it back overboard.
Of course it was all 'legal' when EY did it, with a holding tank and deck pump out.

I like the choices inherent in the factory system in the 80's, but it does involve some extra plumbing and valving. We have that system, matter of fact.

Why not just motor "three miles" off the breakwater and pump out.

If you have seawater flush, flush a lot of seawater through the holding tank while you're at it. Finish with a packet of the product called Odorlos.

But we really need a freshwater flush system here--ocean microorganisms in the system make it stink and clog the head bowl flush system with black stuff. That can be a simple "T" off the vanity sink drain to feed the head intake hose.