I think the third used boat I ever bought came with one of those hoses that attached the drain plug on the oil pan and reached to the transom drain plug hole on the boat.
Up to that point, I had been drawing out the oil through the dipstick tube with a pump, and I was so tired of that system that I was going to make my next boat an outboard. But the hose was such a blessing that I haven’t looked back since. Every boat I buy gets one as one of the first add-on items I install. Now I just warm up the boat on the garden hose like normal, then slip the drain hose out of the transom opening and catch the old oil as it drains by gravity.
I think this system provides a more complete drain than pumping upward from the pan, where the location of the dipstick tends to indicate the upper level of the oil, and makes it hard to get the thin extraction tube down to the deepest depths of the oil pan. The oil drain plug is engineered for, well, draining the oil. You will have to crawl under there once and connect the hose, but the time savings after that are nearly exponential.
If you use a floor jack under the trailer tongue and a level on top of the engine, you can get the boat to sit in such a way that you get a complete drain, which is important because the reason you change the oil is to get all the old oil out so you can add new oil. If you don’t get a complete drain, you’re not getting the full benefit of new oil.
Hose drain kits are around $25, but I’d spend twice that for the purpose it serves. If the new-to-you boat you’re looking at has an stern-drive engine, you might look into one of these kits.