CONTINUOUSWAVE

Now in my 11th year in boating and nearly as long here at CW, but I am still learning things.

One of my boats has two fuel tanks. We want to embark on a range test where we get everything we can out of one of the tanks before we switch to the other.

Is leaning out the engine as the first tank goes empty a worry about engine damage?

-Peter

I run my engine until it starts to stumble, then shift the engine to neutral, and switch over to a second tank.

On my 1988 Revenge 20 W-T the double fuel pick-up tubes are about an inch above the bottom of the tank, so the tank never truly runs dry.

I always ran my tank dry. It does not hurt the engine. If fuel injected, it may be hard to start and probably not the best for the injectors, so I would not make it a habit if EFI.

What type engine is used?

If the engine is an older two-stroke-power-cycle engine in which the oil is mixed with the gasoline fuel, a cylinder that runs out of fuel while other cylinders continue to operate could be running without any oil. On a V6 engine you probably would not notice just one cylinder dropping out. If the other cylinders ran at high speed for some time before they ran out of oil, there could be a potential for damage.

Modern two-stroke-power-cycle engines like an E-TEC, do not mix the oil into the fuel, so the cylinders are still being lubricated.

Four-stroke-power-cycle engines also would still have lubrication as the fuel runs out.

Another factor is the fuel system. If the engine uses a fuel lift pump that depends of vacuum from the engine crankcase, a restart after the engine ran out of fuel could required re-priming using the primer bulb. If the engine has an electric fuel pump, the engine probably can restart without manual priming.

Not a good course of action if a diesel engine. Particularly if the engine sputters for a few revolutions before stopping. Diesel engine fuel injectors depend upon fuel to provide internal injector lubrication and cooling. Mechanical clearances in injectors are measured in 10 thousandths.

A good way to manage fuel is by using a flowmeter and paying close attention to the amount of fuel added to the tanks.