Any ideas?

[creedsduckman]

I'm fortunate enough to have a gas station in town that sells non ethanol gas. I put ring free and fuel stabilizer in both my Yamaha four strokes. I have had zero issues with fuel lines breaking down.

There is a small place about 15 minutes from me that use to sell ethanol free gas, I assume it still does. When there is a gas station 2 minutes away and the boat ramps I use are 5 minutes away I just use ethanol.

 

[calling4life]

Try something simple and free.

Torque on the head bolts, just to cross it off, been an issue for me on multiple occasions.

 

[Sweatliner]

Thanks for the advice. Appreciated. Thought I found it with a loose fuel line clamp. Wasn’t it. Missing bolt replaced, still the same. Hopefully get it in the shop tomorrow

 

[Tyee]

I've got the same engine so I'd be interested to hear what dealer says. Mine cuts out at high rpm but only when I have the low pitch prop on and an empty boat. That's the rpm limiter and it super easy for dealer to check on the puter. You might try some sea foam and also check/change the internal fuel filter. Check the plugs and oil level (oil level on that engine is finicky). I've seen priming bulbs go bad.

Mine runs better on 91 rather than 87. I woulnd't put ethanol in it.

 

[William Reinicke]

Wow.... no mention on spark plugs yet? If fuel has been checked thoroughly, I would be checking spark. Coils, plugs and wires.

 

[Sweatliner]

I’m bringing it in today. When talking to the mechanic on the phone his thinking was it’s the VST ( vapor separator tank ). He said they have had lots of outboards with the issue. I never heard of it, had to look it up. Seems a pain in the *** to remove so I’ll let the pros do that.

Fuel lines, oil, bolts tight, plugs good, everything seems sound. Reading more about the VST sure seems like it.

 

[Tyee]

Mine started coughing yesterday. Pretty sure it was weeds wrapping the prop and causing cavitation in the shallow water. Still, I'd greatly appreciate hearing what you find out. Thanks

 

[creedsduckman]

I've got a 2011 40 Yamaha that has done the same thing to me, or so it sounds like. One time it had a bad coil. The other time it just needed the vst cleaned out. There is a internal filter in there I believe. The mechanic that did it showed me a cup of gas that came out of it that had tiny black specks in it. He said it was the fuel line breaking down, yes it was ethanol resistant fuel line. He recommended replacing the fuel line every other year. I have ever since and haven't had that problem again.

I’m bringing it in today. When talking to the mechanic on the phone his thinking was it’s the VST ( vapor separator tank ). He said they have had lots of outboards with the issue. I never heard of it, had to look it up. Seems a pain in the *** to remove so I’ll let the pros do that.

Fuel lines, oil, bolts tight, plugs good, everything seems sound. Reading more about the VST sure seems like it.

 

[Tuleman]

Mine started coughing yesterday. Pretty sure it was weeds wrapping the prop and causing cavitation in the shallow water.

Keep looking for the cause (cavitation ain't it).

 

[Sweatliner]

Yes. I think you were right. Honestly when you typed that it was a foreign language to me. I should have looked it up. In the shop now. Hoping to get it back for the last few days of the season.