did you check the motor mounted filter to see if it had gas in it. Was the primer bulb soft? Did you remove and drain into a clear container the contents of the spin on filter?
It is unlikely you have enough sediment to make up the space of 15 gallons of gas but you could have 15 gallons of water in the tank, a more likely condition. Regardless, since you filled the tank, you will have a problem if you remove the sender since fuel will spill out into the bilge.
Drain the spin on filter as mentioned, let that sir for 15 minutes and see if there are multiple layers of liquid. If you pumped water into the motor filters and VST or carbs, the motor will never start. The water has to be drained out.
Just remembered: If you pour the filter contents into a glass jar, you may not see different layers, it could be all water. Use your nose and fingers to test.