my step dad has a pneumatic diaphram pump used to change the oil in his 18 wheeler. He tried the oil tube and dipstick one and it didn't work very well. what he is doing now is a long peice of hose attached to the drain plug hole, he leaves this in the boat and plugs the end of it. It takes a little more oil cause of the hose, but it all drains out. with the down the dipstick hose it is hard to get all the oil out. he attaches the big pump to the end of this hose.
the drain plug is the bottom of the pan and it is hard to use that dipstick small hose.