Went from NiMH to 5s Lipo, oh wow!

Just got the boat for Christmas, it's my first foray into RC boating! The boat was pretty dull on Nimh, I clocked it at 26mph with the gps with 2 5000MaH 7.2's and an Octura x642. I then decided it wasn't enough so I soldered on all 5.5mm bullets from motor to esc, esc to batteries, and cut the bec wire and used a separate powerpack. Well, I just put the boat in the water about an hour ago with 2 turnigy packs (3s 4000mah and 2s 4000mah at 40C) and HOLY CRAP, one blip of the throttle took the boat completely out of the water and it did a flip in the air (luckily it landed upright, but it cracked the windshield)!!!!! The GPS wasn't giving an accurate reading, but this boat is simply ballistic on 5s, it's straight up frightening!!!

Questions for ya'll, am I ok running the 40-50c lipos, ESC and motor were only slightly warm to the touch after about 5-10 mins.

I never used 5S on my Fastech before but you are ok 40-50C on 4S for sure.
Ooo, how did you get 10 min of running???

Higher the C rating the better! 40-50C are GREAT, and that motor/esc can handle it fine. Not sure hull limitations though. Sounds like you did everything right with the bullets and dis-ableing the bec. Only thing I would change is the run time- Cut it down to 3-5 minutes and better for the electrics and just a FYI for the future you don't need to cut the red wire to the esc, use a very small flat tip screwdriver to carefully lift the plastic locking tab up on the esc receiver plug and the slide the red wire out and place a small piece of heat shrink on the expose connector, that way if you ever don't wanna run 5s or run a rx pack it takes 5 seconds to hook the bec back up. Other than that great job and get some vid!!!!