CONTINUOUSWAVE

On my 18-footer I have a Yamaha F150 four-stroke-cycle engine and two 12-gallon fuel tanks. How difficult is it to restart if I [let the engine stall by running one of the fuel tanks dry]? I have heard with cars [re-starting an engine that has run out of fuel] is bad.

Turn key to ON position but do not crank. You should be able to hear the fuel pump turn on and pull the fuel in. Cranking is a waste. This is directly from my marina service guy, I have never tried it. The only time I ran out of fuel I kept cranking it until it started not knowing that the cranking was unnecessary.

Go to Walmart and get a "Jump and Go" LiIon jump starter for $60. I used one to start my V8 Suburban, four times, and it did it. Now I have one in each car and one for the boats. The last thing you want is to kill your battery trying to re-prime your fuel system.

Both the high speed and low speed (lift) pumps will run until the proper pressure is reached. Priming the fuel line (squeeze the bulb) will help reduce the time it takes. This is one of the few times a primer bulb actually helps.

There is nothing intrinsic in a four-stroke-cycle engine that causes it to behave differently. No engines run without fuel or start without fuel. Your inquiry is really about priming the fuel system of an engine before attempting to start it. Review the operating instructions for your outboard engine. They will tell you how to prime the fuel system before trying to start the engine.

I've inadvertently run my F70 dry a couple of times--no big deal. After connecting up to the full tank, I used the priming procedure that was recommended by my dealer before the first start (I did the install myself):

--pump primer bulb until hard
--turn the key to the on position (not start) for a couple of seconds to let the fuel pumps draw fuel through the lines and filters, then turn off
--repeat above until the primer bulb stays hard (should only take two or three cycles)
--start motor.

I can't imagine running a battery down during that procedure unless it was about to fail anyway. The whole process should take you under a minute.

The reason they tell you to not run a car out of fuel is the fuel pump resides in the bottom of the gas tank and is cooled by the fuel. And with any pump, it's best not to run it dry. The latter applies to outboards; the former does not.

To run an electric pump dry is bad. Without resistance, the diaphragm can tear. On a steel tank running low sucks in fuel with a higher concentration of debris--definitely not fun for the filter or jets. On an outboard I'll run the carburetors dry when on muffs, and sometimes empty the filter bowl, especially if it'll sit for a couple weeks. Never hurts anything.

He may not have a primer bulb. I do not on my Mercury 4 stroke. It is much harder to prime.

On every outboard I have ever owned, including my 2008 Tohatsu-Mercury four-stroke-cycle 25-HP engine, I have run [the engine until it stalled due to running out of fuel] by disconnecting the fuel line and letting [the fuel line] run dry, and I never had a problem, even when letting the engine sit for months. I just squeeze the primer bulb [until the bulb is] hard. The 25-HP Tohatsu-Mercury engine will start and run in under five seconds. It will run for almost ten minutes at idle with the fuel line disconnected.

rich

Allowing [the engine] to run without fuel to lubricate and cool [the electric pump] can cause damage to an electric fuel pump. If the boat tank is allowed to become empty then no gasoline will be pumped to the VST. The electric fuel pump may become damaged. Some are more lucky or less lucky than others. That is a hefty risk to take by letting the fuel tank run dry.

In an F150 the fuel pump is in the vapor separator tank (VST). The pump is normally submerged in gasoline. The F150 fuel pump is over $350.

Unless you ran out of gas by just not paying attention, why would anyone let the fuel tank run dry on a truck?
rich

Binkster wrote:Unless you ran out of gas by just not paying attention, why would anyone let the fuel tank run dry on a truck?
rich

On a truck, would either be from not paying attention or from trying to stretch the range just a bit too much. I have started sweating a time or two wondering if I will be able to make it to the next gasoline station.

On an outboard motor, [to run out of fuel] might be from someone wanting to use up all of the fuel before they switch tanks. A risky proposition with an EFI motor.

I just read the owner's manual to my new automobile. Here is what they say about running out of gasoline:

RUNNING OUT OF FUEL
Running out of fuel can cause damage not covered by the vehicle Warranty.
If your vehicle runs out of fuel:

• Add a minimum of 1.3 gal (5 L) of fuel to restart the engine. If your vehicle is out of fuel and on a steep slope, more fuel may be required.
• You may need to switch the ignition from off to on several times after refueling to allow the fuel system to pump the fuel from the tank to the engine. When restarting, cranking time takes a few seconds longer than normal.