Air leak in fuel line?

[VolFan]

So Saturday AM I started the boat as normal after disconnecting the fuel tank to take it to fill up. 6 gallon tank to a 2015 Mercury 20 hp 4 stroke. Quick release at the motor and quick release about two feet from the tank. Primer bulb and fuel demand in line. I thought I heard an air hiss as I primed it but started as normal and off I went. At full power it felt like it throttled way down to idle. It would then throttle back up if I backed it down and back up and then the same thing would happen. Vent was open on the tank, fresh gas. Any thoughts? 

[airshot]

Not sure I follow what lead up to your issue.  Fuel connectors on tight, any damage to orings on the connectors??

[ElGuapo928]

I change the female side of my quick connect about once a year - similar symptoms, throttle decels and surges.

 

I just chalk it up to a mix of weird fuel chemistry and poor QC on the o-rings/seals from China/India/whoever is cheaper. Also carry a spare quick connect set just in case it decides to go outside of the usual February maintenance ritual.

[VolFan]

I disconnected the tank to fill it - that’s the only change. These fittings are 5+/- years old so it’s probably time to change them out. 

[casts_by_fly]

3 hours ago, VolFan said:

I disconnected the tank to fill it - that’s the only change. These fittings are 5+/- years old so it’s probably time to change them out. 

 

If the fuel lines are that old and not OEM then I'd just change them too while you're pulling it apart.  A pinhole is enough to make for a tough day and you never know when one will pop in.

[Skunkmaster-k]

Methanol strikes again. 

[airshot]

With the poor quality of todays fuel lines a tiney crack in the line could create that.  I replace mine when they get stiff.  Soft and pliable is ok.  I have also found that the ends of the fuel line become set and stiff where the fitting is attached.  At the start of the season, I often trim the ends back an inch or so to get into more pliable line which creates a better seal where the fitting is clamped into the line. Unless your fuel hose is really old, it will be alcohol resistant, all fuel lines in the past...at least, 10-15 years are alcohol proof. 

[WRB]

2 hours ago, Skunkmaster-k said:

Methanol strikes again. 

Ethanol is added to gasoline.

Tom

[VolFan]

The fuel line is still in great shape - I will replace them anyway out of an abundance of caution. I think I probably have a fitting that’s going bad or I smushed one or caught it in the hatch door. I just wanted to make sure it was symptomatic of air in the line - thanks everybody!

[airshot]

Those fittings use O rings that do go bad. I have replaced many omc O rings in the past but now have Mercury and not sure about these.  However, new fittings are not that expensive, actually much cheaper than having to be towed in !!