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Yamaha 70 hp 15 sec stall

R

rcosta

New member
Hello,

I am getting my engine going for the spring. It starts up right away but stalls around 15 seconds. Just before it stalls, it shakes a bit and it sounds like air either being brought in or let out. I winterized the gas last fall but noticed the gas in the small gas filter was brown. I pumped it out until clear gas is going through but it still stalls after 15 seconds. Certainly seems like the gas is being cut off but I am unsure where at this point to look.

Thank you.
 
Sounds like fuel starvation to me too: starts on the fuel already in the rail, runs for about 15 seconds. The brown fuel in the filter confirms contaminated fuel was sitting in the system all winter. The air sound could be the fuel pump losing prime or an air leak in a fuel line connection IDK?

Did you check the VST internal screen or the injectors? After a winter sitting with oxidized fuel, those are almost certainly gunked up. The VST screen is the most likely culprit for a hard stall like this, but the injectors were soaking in that too.
 
Thank you for this. I just watched a video on VST filter changes so I might try that next weekend.

I was just working on it and verified that the gas going through the engine now is clear. But I am noticing when I pressed the ball to get the gas into the engine, it never hardens. And the engine still starts right away and stops after 15 seconds. And then there is an audible air hiss. So it is getting enough gas to start but then consistently after 15 seconds, seems like the gas is getting cut off.

Does this still sound like clean VTS filer issues?

Thank you again.
 
Nice find! If it never gets firm and holds pressure, you've might have an air leak on the suction side. The engine starts on the fuel already in the rail, runs until that's gone, and then starves - does the hiss you are hearing sound like air entering the line? Probably around the bulb area?

I've had the same thing happen on a 20 year old Range Bass boat. Primer bulbs can develop small cracks or the internal check valves going bad. They look fine on the outside but leak air and as soon as air gets into that fuel line it will shut down the engine abruptly.

Replacing the bulb is a cheap and little bit easer fix that exploring the VST filter.

BOAT - Break Out Another Thousand!

Good luck.
 
Thank you. I just ordered a new fuel line with a bulb that I can check next weekend. Not only cheaper but much easier than the VST so I will start there.

Am I correct thinking that if the VST was clogged the engine would not shut down every time after 15 seconds? I would think a clogged VST would make the shutdown sporadic? Does that make sense?

Thanks again.
 
See what others have to say, but I tend to agree with you if it's like clockwork. It's hard at a distance and in the forums. I know everyone does their best to give good advice, but it's difficult without having hands not he outboard. Sounds like fuel is getting into the rail, it's burning up, and then the issue is with the new fuel delivery.
 
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