Fuel starvation

[Quentin Withfield]

Hi guys I have a question.
I have a mercury 125 and straggle with fuel starvation. I even added a in line electrical pump but still when the tank goes below half the system runs dry. Can anyone help

 

[Seastoke]

Air

 

[Davy_S]

Mercury Fuel Pump Diaphragm Kit

 

[QBhoy]

Hi. Not to be the smart arse, but what you have described, can be typically caused by one or more, of a handful of situations.

Most common of which might be;

A misguided or inaccurate fuel gauge
A poor breathing or non breathing/venting fuel tank
A blocked fuel filter (primary and secondary should be considered)
A compromised quality of fuel in tank…as a result or influence, of water contamination.
A restriction or reduction of the ability of fuel to easily flow, caused by a blocked pickup pipe, non return valve or anything else that might suffer as a result of a lesser head of pressure having an influence.

Jeez..without knowing or experiencing exactly what’s going on, it could be a load of things. I’ve even known it for some guys to suspect fuel starvation to be the culprit, of such a thing…but it actually turned out to be as a result of battery or sustainability of charging issues. The notion of having been out and running for a few hours, or fuel levels getting low, often far too easily suspected instead.
But most likely, and at a quick assumption from a far..it’s going to be a fuel delivery/breathing issue.
Tell us more about the fuel system. Remote, portable or inbuilt tank ? Primer bulb ? In line filter under the hood ? Pre filter inboard and in the boat ? Primer bulb in line ?
Or perhaps most telling of all…is she an optimax, fuel injection or even a 2+2 carb ?

 

[Quentin Withfield]

In-built tank: yes.
Primer bulb: yes.
Filters: 2 inlines.
Carb 2+2
Replaced pump kid 10 hours running time+-

 

[ChromeDome]

Test a different tank.

 

[Quentin Withfield]

Thanks for your help with this problem I will test all your suggestions and give feedback

 

[Milgrip]

Hi guys I have a question.
I have a mercury 125 and straggle with fuel starvation. I even added a in line electrical pump but still when the tank goes below half the system runs dry. Can anyone help

Not familiar with your engine and this can be a fire hazard so beware. Use common sense when messing with fuel. Remove kill cord, disconnect fuel line from pump to carbs, spin engine on starter and see if fuel comes out of pump. Now you can work forward to carbs or backwards to tank eliminating items in between.

 

[snowbird30ds]

If using a portable tank I've had similar on a small outboard and after many strips of pump and carb and replacing bayonet fittings found the pickup pipe in the tank had a hairline crack halfway up letting it suck air, it seems the plastic it was made from couldn't handle modern petrol, once replaced issue went away.