I have a 2001 V-18 with a 150XR6 and haven't seen any cracks developing around any of the corners or welds. There are pictures in my library, and photos of the motor in the Grab Bag section under Lower Unit Oil Change.
I don't know what the difference in weight is between the carbed XR6, the EFI or the Optimax but I'm guessing the Opti weighs quite a bit more. You may want to check.
Mine is rigged stock with a 23-inch Black Max 3-blade aluminum, which is too much pitch. It tops out around 5200 rpm and 54 on a GPS in smooth water and a FULL tank with a FULL load of gear. I've had it up to 58 empty and almost an empty tank. At some point I'd like to try a 21-inch Tempest stainless, or a 21-inch Black Max and raise the motor height a bit just to get the RPMs up to the engine's rated max of 5800.
Quite honestly, I wouldn't mess with a jack plate. I don't think you'd gain that much and the boat really isn't designed for one. It doesn't have a pad, and the step notch from the primary transom to the keel is only 4 or 5 inches.
Washover isn't really a problem. You'll get the back deck wet, but the only way I've ever buried the transom is to back up hard in reverse. You can put the deck under that way.
The difference between the '01 transom and the later boats is that the 01's transom has wood sandwiched between the inner transom bulkhead and the outer bulkhead; the later transoms replace the wood with aluminum cross-braces welded in several places.
My '01 is very stable running WOT if the water is smooth. In a good chop the ride is dry. If the lake has rollers or a lot of other boat wakes, I don't recommend running WOT. It' hurts too much.
One other thing: I've noticed that I need to tighten up the motor bolts once or twice a year, and I suspect its due to torquing when applying the throttle to get out of the hole. They've never been loose, and the motor doesn't get to the point where there is play between the mount and the transom, but the bolts aren't tight.
