Today was fairly productive. This morning I broke down the 150 and transferred the water and live rock into the old 100 and a spare 40 gallon brute. The 100 looked puny compared to the 150. Was actually kind of nice how little space it took up. Would have been tempted to leave it in place if the 150 did not leave me so much more room to play.
Once the 150 was empty I began to cleanup the area for the new bulkhead. I was going to put in adjacent to the existing bulkhead, but that area while flat, is not recessed and would have stuck the plumbing out a few extra inches.
I started by trimming off some raised ridges around the old one. At first I used a chisel to cut the extra off. Worked well to a point and then switched to an undercut saw. That worked very well.
To cut the hole I purchased a new hole saw as all of mine were too small. Tried cutting a guide in a board to lay over the desired location since there was a smaller existing hole. No matter how I tried to work it, the kickback just jerked everything around and I would have ended up with a badly nicked surface. Decided to take Andy's suggestion and try my RotoZip. Never really used the thing in 6 years, but it worked like a charm. Drew a circle around the bulkhead with a Sharpie and then zipped around it freehand. Did a nice job in about 30 seconds.
Took it outside and sanded it all smooth. After a good wash down, brought it back in and installed the new 2" bulkhead. For good measure I put a bead of silicone around the inside and outside. Let it dry for a few hours and then filled it with a few inches of water for a leak test. No leaks!
Got everything except for the skimmer back in place. So far the only leak is a few drops of water inside the bulkhead. That is just coming from the temporary plug. Another quarter turn on the plug should fix that.
Hopefully over the next few days I'll get the plumbing hooked up and be ready to fire up the new pump.