This is a great thread! I replaced the impeller on my 268 Vista with Mag 350 today and this was a lot of help. I can tell you on a Vista it is a bastard. I did it in less than an hour, but because of the hump for the aft cabin in the starboard cockpit area, you have to access the pump from the opposite side of the engine...I have pretty long arms and was able to lie across the engine and sort of stick my head and arms down the hatch in front of the engine, but it makes for a bad angle to try and reach behind the pump to get the inside bolts loose on the back of the pump. Without the pics in this thread, it would have taken forever because I was working mostly by touch...at least after looking at the photos, I had some idea of what I was groping around for. It's done now, so hopefully I wont have to do it again for awhile. I ordered a spare, but I think the chances of me trying to change one out in the bay with everything rocking like crazy and engine fairly warm is outta the question. I'll definitely be calling sea tow...
Also wanted to add that a 10mm gearwrench works WONDERS for those six bolts on the back side of the housing. Thanks again for the GREAT info on this thread!