Does anyone know where I can buy a 14'-15' fuel line for a Yamaha?
Or is it legal to splice more length in the hose, keeping my original hose and connections?
Moler makes a 12 footer ready to accept the right fittings but that doesn't seem like it will fit the bill for you. I don't see any reason why you couldn't buy a double ended hose barb, a couple of high quality hose clamps (the ones with the little shim that makes sure that they stay round) and the appropriate length of fuel line to extend the one you have.
Alternately you could harvest the ends and bulb off of your current one and buy enough fuel line to build the length you need.
Well, they have special clamps that have no way of taking them off without destroying them. That got me to thinking that maybe they don't want you disassembling them and it would be against some law.
I have my fuel tank mounted up front and used coated steel line, in my case I used 2 10' pieces with hose barbs on the end. I then used 5/16" rubber hose to connect the solid fuel line to the tank and the motor. I have the primer bulb in the rear by the motor. Remember to leave enough rubber fuel line at the motor to allow it to turn, I learned this lesson the hard way.
For clamps I just used normal stainless screw clamps. You can get a primer bulb at with plastic barbs on the end of it. I got mine at the local Mercury store.
You can make a hose to any length by purchasing a primer bulb with barb fittings, a quick connector for either end, your length of hose, and 4 hose clamps.