Re: 79 140hp Johnson hard start
The filter can be dumped as often as you want or some models have bottom drains.
Coast Guard regulations require that built-in tanks have anti-siphon valves on the outgoing fuel fitting, where the outgoing fuel hose is connected. This is to prevent the fuel from being siphoned from the tank if there is a leak at the hose or engine.
Most anti-siphon valves are of the type that have a ball bearing with a spring. The older ones are designed for inboard type installations, not outboards, and they are not designed for today's fuels. In addition, they are prone to sticking, causing poor fuel flow.
Regardless, the fuel system has to overcome the pressure of the valve in addition to lifting the fuel.
The bottom line is that if all of the outgoing fuel lines and the engine are higher than the top of the tank, the anti-siphon valve can legally be removed. If not, it is good practice to replace them with the newer ones.
If you take the tank fitting off and find that there is no valve inside of it, you can move on to the fuel line and bulb and so on.