Nick,
I added a drain hose to mine a few years ago. They are now standard on a lot of the Mercruisers. Leave the cap on and stick the hose through the transom drain hole. Get a container and take the cap off. Get the end of the hose as low as possible. Of course the engine should be warm for the best results. When mine is just about done draining, I add another 1/2 qt of clean oil to push out as much of the old oil as possible. I like this system because most of the mess is outside the boat. You may still get a small amount of oil in the bilge when you remove the filter. Make sure you put some oil on the new filters gasket surface, so it will seal and remove easily.
You don't need a pump. The oil drains by gravity. There is not a valve in this system. The oil will drain real slow even when warm. The I.D. of the hose is quite small.