Johnson 90 Four-stroke Stalls

[TransFueler]

Greetings--I'm a relatively long-time (47 years) boat owner that just got my first Boston Whaler, which is a bucket list thing for any boater.

We also have a Wooldrige outboard jet sled for river fishing, and have owned a wide variety of power and sail boats over the years. I also mess around with vintage British and German sports cars and vintage race cars.

My Whaler has a 2003 Johnson-Suzuki four-stroke-power-cycle outboard. I've only had it out a few times. It sat in our barn for a couple months before I took it out this week. Unfortunately, the boat left my son and I dead in the water a mile or so from the launch ramp.

[The boat] had some sort of old gasoline in the fuel tanks. I stopped on the way to the lake and topped off both 12-gallon tanks. [The 90-HP Johnson engine] started up at the ramp. Fuel injection is a beautiful invention.

About three minutes from the ramp, the engine died. Fortunately, it was only because the tank-to-engine fuel line had come off the motor. Stuck it back in and off we go. Sadly, a couple minutes later, the RPM gradually wound down, and the engine died again, like I slowly brought back the power, not a sudden stop.

Tried to restart. Almost caught a couple times. but no run. Got a guy to tow us back to the ramp. Towed the boat home. Pulled the engine cowling--everything looks totally normal. Squeezed the fuel hose primer bulb and plenty of fuel there. I think an ignition or electrical problem would have had an immediate cut off, not a gradual loss of RPM. But what do I know, I play with ancient British cars.

Before I take it to a good local shop, naturally I would like to resolve this myself.

Sounds like a fuel problem to me. I'm not remotely an EFI-four-stroke-outboard mechanic. My plan is to replace the fuel filter and see what happens. Any other bright ideas before I submit her to the professional outboard gurus?

[dtmackey]

With the introduction of E10 fuel, I normally start [looking] there [for the cause of running problems] if I can confirm the engine has spark. On the fuel-injected engines there is a lot of fuel hoses, [vapor-separator-tank], pump, and injectors, and bad fuel will take some time to work through. Adding good fuel to the tank may dilute the bad fuel--make it a little better--but it takes a while to get to the motor where you'd notice a difference.

As for fuel with ethanol it does not last like the fuels of yesterday. I've read articles where it can lose up to 1-octane point per month depending on the fuel system setup and environment. Does that mean you lost all those octane points? Probably not as that is worst case, but it does raise concern. If [the fuel tank] can be closed (vent shut), do this during storage. It's also good to store fuel [tanks] full or completely empty, and treat with a proven E10-treatment and not one of the snake oils at the auto parts store.

D-

[jimh]

I agree with your supposition that the cause of the running problem with your engine stalling is likely related to fuel because the onset of the engine shutting off is prolonged and slow.

To diagnose the cause, try getting a separate tank of gasoline with all-new, fresh gasoline. See if the engine runs on that fuel

The state of the primer bulb can be a useful indicator for diagnosis of the fuel system. For advice see my article:

A PRIMER ON PRIMERS
http://continuouswave.com/whaler/reference/primer.html

Fuel flow can be obstructed by fuel filters that are filled with debris. Check any in-line fuel filters.

Water in fuel is also a problem. Check that there is no phase separation in the fuel tank, with fuel floating atop a layer of water on the tank bottom.

[jimh]

Because the engine seems to be able to run normally at time, I don't think the problem is in the engine's fuel system. The problem is likely in the boat's fuel system. There may be an air leak or an obstruction in the fuel hose or in the fuel tanks.

[TransFueler]

I drew a pretty good size sample from the Fuel Vapor Separator.

In a 9-inch-diameter bowl, I got an inch or so of water, and about two inches of gasoline. I drained both fuel tanks and am letting them totally dry out. I bought new low and high pressure fuel filters and will install them tomorrow. I will drain the fuel rail as well, and try it with fresh gasoline fuel. Hope I don't have to remove and clean the FVS [fuel-vapor-separator]; you have to remove the intake manifold to do that.

[dtmackey]

[Water in the fuel system] could explain the problem: after the engine ran for a little, the water mixed with the fuel and killed the engine. Work through the entire fuel system so there is no old fuel left. You may want to install a Racor filter with water separator bowl for peace of mind; those are less effective with the current E10 fuel but do help.

Jim brought up some great points, while I was focused on the fuel itself. It would not hurt to make sure the primer bulb is functioning properly and not collapsing when the motor is running. I've found the cheaper bulbs are not worth the money and now run only Yamaha bulbs, even on my non-Yamaha motors. Also make sure the fuel line has not laminated on the inside (inner wall separation) which leads to collapse under vacuum. On boats with built in tanks, it's good to inspect the check valve as those can fail over time. Some people remove them, but the USCG requires them.

Hope you report back with good news.

D-

[jimh]

Re the fuel line hose: if you have any fuel line hose with a gray metallic outer cover, get rid of it. Change to fuel line with a black rubber outer jacket and rating of A1. The gray metallic jacket fuel hose is notorious for delamination of the inner wall liner, causing obstruction of the fuel passage. See

INTERPRETING FUEL HOSE RATING DESIGNATORS
http://continuouswave.com/forum/viewtopic.php?f=6&t=2897

[TransFueler]

Thank you. I did not know that. Installed new filters today. Will go get some new fuel line and fittings tomorrow. Might as well try to do it right.