I've just spent an hour and a half removing the raw water pump in my Bav 30. What a nightmare of appalling lack of design for serviceability!
As it's not a particularly durable item, there may be a few forumites who need to remove it at some time. Let me offer a little advice to anyone trying it.
First off you need to remove the bottom step of the companionway, but you probably know that anyway because it's the easiest way of changing an impeller.
Now, as you look on the front of the engine there are four fixings securing the pump. Those at NW and SW are nuts and bolts and only meet the description of "inconvenient". AT NE and SE are two bolts with their hex head facing away from you running into a threaded hole in the pump body. One of these is "king difficult" and the other is "apparently impossible".
I began by just loosening the two nuts and bolts and then turned my attention to the other two fixings. Using the ring end of a 10mm combination spanner (a normal cranked ring spanner wouldn't get in there) I worked at the SE bolt 1/12 of a turn at a time, accessing from underneath. It took a horribly long time as there were several threads protruding beyond the pump body so it probably took about 8 full rotations of the bolt.
The key to removing the last bolt (NE) is to fully remove the two nuts and bolts first as the space where one of the bolt heads sat is th only space that allows enough room to swing the spanner. Again it's 1/12 turn at a time so reversing the the spanner at each move. You can't see what you're doing and you can barely feel it either because there is no room to get any other fingers in. Finally though, it all comes off. Phew! Now I just have to change the seals and put it all back on again.
I hope that helps someone. (Even if it only persuades them to give the job to a mechanic.)
