# F40 starving or flooding



## SquiggyFreud (Apr 18, 2014)

Hi all had a problem today.  

Yamaha f40...40 hours on engine. Fresh gas put in tank today.
Ran great for 45 minutes then started bogging down when trying to accelerate. Could only go 3 mph after that.

I could squeeze bulb and it would get firm, but after running engine briefly it was quite soft. I tried closing vent, opening vent, cap off of tank nothing helped. When I would remove the fuel line from engine a bit of gas would squirt out. Could not even rev up engine in neutral without sputtering. When I got back to the dock (Got towed) it would rev up again, but was ready to get outta dodge.

I suppose I will start by changing fuel line and bulb, and check to make sure screen is clean in tank.

Any ideas you all?


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## ccm (Apr 19, 2014)

I would say that your either sucking air or you got bad fuel. You said you were going to replace the fuel line. If its still falling flat after replacement then that is not your problem and you have a good spare line. If it was a lot of fuel Don't throw it away without testing it first ( lawn mower, weed eater, etc... ) If it wont run in these you got bad fuel. All else fails consult your dealer.


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## SquiggyFreud (Apr 19, 2014)

I emptied and inspected on board fuel filter, as well as fuel water seperator. Both looked fine. Bowl filled up quickly when I pumped bulb, but bulb is soft again in less than a minute. Going to change fuel line and bulb then take her for another run.


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## turbotodd (Apr 19, 2014)

You didn't say what year the motor is, or whether it is EFI or carb. The carb'd motors were either 3 or 4 cylinder, the very early carb'd ones were 4 cylinder (and my favorite)-same powerhead as an F50.

The early F40 EFI motors had an issue with the VST fuel pump, and were recalled by Yamaha. The ones that had the recall for them would exhibit the exact same symptoms as you're describing. 

I'd suggest calling the dealer with your PID (serial # of the motor) and see what they say about it. 

If no recall, and it's an EFI motor, the pump screen (sock) is probably obstructed. That or the pump is failing. Or injector screens plugging. Have seen them all 3 ways and 99% of those times it was caused by old fuel. EFI is awesome but the fuel has to be kept clean just like a carb'd motor. Bad part is, a carb motor coses about $300 to clean all 3 carbs. EFI motor, double that and then some to do the pump & replace injectors. They can be cleaned if you have a local injector cleaning company-but make sure they have a guarantee.


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## SquiggyFreud (Apr 21, 2014)

it is a 2012 EFI... I always use fresh gas, ethanol free. The station I use is quite busy, so I doubt the gas stays in their tanks for long either.I have changed the fuel line, will remove remaining gas put it in my car and try again with fresh fuel. If it happens again, I guess it is time for a trip to the dealer.


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## JL8Jeff (Apr 21, 2014)

When the fuel pump diaphragm went bad on my old 99 Johnson 2 stroke 40 hp motor it acted the same. I swapped out tanks, fuel lines, filters and it was the same. I could squeeze the bulb and keep it running good but you could see the fuel was not refilling without me squeezing the bulb. I went through 2 fuel pumps in a couple of years, I think it's the ethonal eating away at the rubber components. I got a rebuild kit and it ran fine after that. With yours being EFI, I wonder if it's fuel pressure related or injector related. It sounds like it's not pumping fuel.


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## SquiggyFreud (Apr 22, 2014)

Yeah I think it is fuel delivery related...I have one more section of fuel hose to change...from the fuel/water separator to the engine. A friend suggested I check the spark plugs, which I will do, but I still think it is fuel line or pump.


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## fzr1kg (Apr 24, 2014)

Having just had six months of issues with the same motor I can tell you that there was a tsi issued for your motor and it needs Yamaha to service the VST.
The motor I have stalled, spluttered and near killed the wife and I twice. Once by stalling on St Andrews Sound in gale conditions and breaking seas pushing us towards a shoal, the other by stalling mid channel long enough for a cargo ship to start being a real threat.
We managed to get it started both times and got out of it.

I'm at the marina where we bought the motor from in September last year and it's taken since last Friday till now to get it resolved. Apparently even though it's under warranty, I'm still meant to cover part of the bill. I'll be finding out in about 10 minutes just what Yamaha has decided to do about it. Will report back.

Changing the pump and regulator on the VST seems to have fixed the problem. The engine now sounds like it did when new.


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## Rat (Apr 24, 2014)

Scary stuff...
What is VST? I'm guessing it has something to do with the fuel system?


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## turbotodd (Apr 24, 2014)

VST=vapor separator tank. It's a tank mounted on the side of the motor that contains the high pressure fuel pump, regulator, float and float valve, among other things. EFI motors have them since there's no reliable way to mount a high pressure pump inside the boat's fuel tank.


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## SquiggyFreud (Apr 25, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=350005#p350005 said:


> fzr1kg » Yesterday, 15:21[/url]"]Having just had six months of issues with the same motor I can tell you that there was a tsi issued for your motor and it needs Yamaha to service the VST.
> The motor I have stalled, spluttered and near killed the wife and I twice. Once by stalling on St Andrews Sound in gale conditions and breaking seas pushing us towards a shoal, the other by stalling mid channel long enough for a cargo ship to start being a real threat.
> We managed to get it started both times and got out of it.
> 
> ...



Where can I get the info on this recall/issue? I just checked the Yamaha site and see only 1 recall for the F40, and it relates to the fuel tank fitting.
Mine is a 2012 model F40LA


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## SquiggyFreud (May 8, 2014)

Picked her up from the shop yesterday. Turns out the recall was on the engine fitting, I thought it was on the fuel tank side. Anywho, the mechanic put the old style connecter on the line and said it is running fine. Ready to take her out for a run!!


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## SquiggyFreud (Jul 23, 2014)

The fuel fitting did not fix the issue, I had to take it back to the shop one more time. This time they ran it in the water and got stranded. :LOL2: 

Fuel pump kit was changed out and since then she is running great! I have put 15 or so hours on it without a hiccup!


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