It sounds like the seal of butyl around the flange is leaking. You should be able to remove all the screws around the flange and work the water heater out a few inches. Do not use silicone as this is not the best to seat this with. Instead clean of most all of the old sealant and get some new butyl tape and apply to the flange. Re-secure the water heater and you are done. You should have enough lp gas line and water line play not to have to disconnect. If you don't and disconnect these, be sure to check for leaks after reinstalling. It is especially important on the lp gas line connection. Use a little Dawn and water solution around the fitting with the lp gas tank valve open. Good luck and keep us posted.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7