'96 Evinrude 9.9 HP Four Stroke stalls after 20 minutes EVERY TIME!

Greetings!

I have a 1996 Evinrude Four Stroke 9.9 hp outboard that runs perfectly for 20 minutes and then acts like it's running out of fuel or getting erratic spark. Here's a video https://youtu.be/uWYP8zWlPCs.

I've replaced ALL electronics, including stator and coil. I've rebuilt the carb, new thermostat and plugs, new impeller, new hoses, new fuel bulb, connectors and hoses, cleaned all electrical connections, and still the engine craps out after twenty minutes.

I've tried squeezing the bulb, nogo. It's pissing good water flow. I'm at a loss!!!

I put the motor in a barrel and ran it in gear for an hour at medium rpms and it never failed. But when I put it on my boat, it fails within twenty minutes every time. If it rests for five minutes, it will start up and run for few more minutes. The longer it rests, the longer it will run, so I suspect a heat related issue.

How do I troubleshoot this?

Thanks,
Mark in Leander, Tx.

Run with a known good fuel tank and hose.It sure sounds like a fuel issue , but run with a timing light hooked up to see how spark behaves when motor falters.---------------Oil pressure has been looked into ?

racerone said:

Run with a known good fuel tank and hose.It sure sounds like a fuel issue , but run with a timing light hooked up to see how spark behaves when motor falters.---------------Oil pressure has been looked into ?

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Thanks for the reply racerone!

I have an external fuel tank with the original connector, so I'll definitely replace the o-ring in the fuel tank connector! All other fuel lines are new. All metal clamps are new and tight. I haven't checked the oil pressure, not sure how, honestly, as I don't recall seeing any kind of gauge. I'll verify good oil level and get a timing light for my next trip out.

Thanks again!
Mark

With what little fuel that engine would burn, it would be my guess that a fuel restriction exists with the tank you're using, vent not open, something of that nature, and the engine is indeed running out of fuel... UNLESS... you've already switched to a different tank and double checked the vent already.

Thanks for the reply, Joe.

I agree that it is most likely a fuel restriction issue. It's not the tank cap vent as I know it's open when I run the motor. I have new connectors on both ends of the fuel line from the tank to the motor, but I haven't verified the integrity of the fuel tank connector itself, so I'll take a hard look at that. Or get a new tank and not worry about it.

One thing I neglected to mention.... There have been occasions when the outlet valve of the fuel primer bulb would have the valve retaining cap come loose and fall to the inside bottom of the fuel bulb, then as the engine runs the inner portion of that outlet valve would fall out and eventually get drawn back into the valve shell... BUT... it always gets drawn in backwards due to its design.

This effectively creates a fuel shut off valve.

This may not be your problem BUT it has been known to be one of them.

Thank you for that info. I would have never thought of that. It's a new bulb, and the issue is consistently after 20 minutes of motoring, so I'd say that the probability is pretty low. But thanks anyway!

Did you ever put a timing light on it to see what your spark is doing when it fails ??

Not yet. I replaced the power pack last week and it seemed to fix the problem. It ran almost an hour against a strong headwind, then started acting up a bit, not as much as usual. I ran it again yesterday and it failed at 20 minutes like it was doing before. I have to find a timing light and try that next.