I just replaced the 12 year old diesel fuel tank sending unit in my 2000 H340. I contacted Hunter Marine for advice on which model they have installed and they told me to get a Teleflex replacement. However, when I removed the old unit it was a Moeller/Tempo design, with the float arm attached to the underside of the top of the unit. The tank is 13 deep so I replaced the sending unit with a Moeller # 35722-10; with a 12” long arm. They make a unit for a 12 to 24 tank but I used the one for the 12 tank since the float arm hangs vertically down and will indicate an empty tank just as well. When I installed the unit it read the correct tank volume. The rubber gasket and new bolts comes with the new unit so you dont need to order a separate one. The original bolts are coarse thread so I reused the old bolts. The polyethylene tank on my boat has the mounting nuts embedded in the plastic. The gasket and the sending unit have asymetrical bolt holes so the unit can only go in one way, so check the correct alignment before you position the unit. The float arm inserts and swings toward the forward end of the tank and the sending unit itself was correctly aligned as received from the manufacturer. Hunter did not use any sealant under the gasket so neither did I. Before installation, I noticed a small pool of water on the top of the tank and traced a small leak to the bolts that hold my arch to the cockpit coaming. Water drips into the compartment and then down onto the top of the tank. After sealing the leak, I put some caulking around the edge of the fuel tank sending unit to prevent any future water from entering the tank.