Yup - first time I tried to pump out, the marina didn't have a fitting that would fit (and they had at least half a dozen of them for various boats). I paid the guy $20.00 to go to a nearby boat storage facility and borrow their tapered rubber adapter (hold it down TIGHT! 😱 ). As soon as I got home I made up several configurations out of black polypropylene threaded fittings (90, 45, & short straight) to the marine male camlock fitting (get the smaller 1 1/4" MPT, 11.5 tpi size). I thought keeping everything all black was appropriate. 😉 BTW - they almost float - so I added a keychain floatie to each of them (trust me, you want them to float) - now they barely float.
The second lake I went to only had RV gravity fed dump stations. So, as soon as I got home I made up a 3/4" hose, fitting and adapters on both ends (pieced together from replacement parts from Valterra SewerSolutions kits for RVs) to connect the boat's overboard discharge fitting to an RV dump station. I do not use the added water hose hookup feature - it works GREAT (takes about 3 minutes to pump out a full tank, uphill!) I store everything in the propane locker.
However, I'm still not thrilled with the through hull fitting connection. So, I plan to add another Jabasco Y-valve and use a quick disconnect to the sewer hose I already have (I have everything I need, except the time to install).
I won't be hauling my crap back home again.
BTW - I take no credit for designing any of this. I got all these ideas from others on this forum (I'd give them credit here, but I don't remember who they all are). SEARCH is your friend. Good luck.
Todd