On a related method of figuring out leaks from water tanks----and I owned a Formula 350 CBR----but this is how we fixed the polyethlyne water tank in his sailboat.
First, we ran the tank and pump dry or at least to make sure the front water tank was empty since we suspected it was leaking. Then we used a shop vac to vacuum up all the water in the bilge so we could make sure it was dry. Then we mixed some blue food color up in a 5 gallon bucket and filled the tank since we had determined the leaks weren't coming from the hoses we could see. Since we then carefully filled the water fill with the 5 gallon of blue water and waited and watched. It was easy to see it wasn't leaking from the fill lines. After a short while we could see it was coming from the bottom of the tank or at least coming out from somewhere underneath. We then ran the pump and pumped out as close to 5 gals as we could. We then removed the tank and found a crack in the plastic where it rested on a stringer. Beneteau wanted $1400 for a new tank. I found him a plastic welder near where I live. I really quizzed the guy to make sure we weren't going with a cheap ass fix. It cost $60 for the guy to plastic weld it up. Upon reassembly, we put rubber strips down as pads to prevent wear from stringer into the polyethylene tank. 2 years later and $1360 in savings later, it's all good. I didn't help you remove your tank yet, but just to see if you can track down better where the leak is coming from using colored water which you can suck back out. Good luck.