8hp yamaha outboard issues

[Noah Fitzpatrick]

Had the boat out the other day, got 1k out from the ramp, and the motor cut out suddenly, and then wouldnt start for 5 mins. It happened about three or four times again before i called it and went back in. Noticed that the primer blub was struggling to pump fuel, and was very slightly sucked in when i was moving. Valve on the tank was open so it wasnt causing a vaccum. I could prime it but it was a lot harder than usual, and then it would run for another minute or so at full throttle before chugging and then dying again. Has this happened to any of you? I am thinking either a blockage in the fuel line, dodgy fitting on the tank end, or possibly a blocked/dirty fuel filter???

 

Thanks in advance.

[Bretto77]

Pre filter???

[Bretto77]

I don't know your set up but it sounds initially like a filter issue.

[Bretto77]

Before the primer bulb.

[Bretto77]

Is the vent valve on the tank actually doing it's thing??? Loosen the fuel cap to see if it makes a difference?? 

[Noah Fitzpatrick]

it feels like the vent valve is doing its job yeah, air is being let through, but maybe the issue is that its not enough, i will look at it

 

[Noah Fitzpatrick]

35 minutes ago, Bretto77 said:

I don't know your set up but it sounds initially like a filter issue.

its a pretty simple motor, by the looks of it, only one fuel filter which leads directly into the motor basically

 

[Bretto77]

Sounds like the motor is trying to draw fuel with restriction before the motor somewhere.

[Noah Fitzpatrick]

yeah thanks brett will have to do some more investigating

 

[Angry51]

Yeah, sounds like a filter issue.

[Noah Fitzpatrick]

was just having a think, possibly an air lock in the fuel line?? Maybe if i take the clamp and fitting off and pump fuel through i might be able to get it out if thats the issue. Filter seems unlikely seeing as it was just recently serviced and replaced.

[Bretto77]

Could even be a stuck valve in the primer bulb. But I would be checking everything from the fuel pick up in the tank right through to the motor. 

 

[Angry51]

Yeah, even fractured inner casing of fuel pipe folding over and causing a blockage. How old is the fuel line.

[Noah Fitzpatrick]

fuel line is basically brand new so doubt that is the issue

 

[Angry51]

Was just a thought, have seen it happen.

[mangajack]

Starving for fuel.....external breathers away from the tank might operate well at the breather but not down the line at the tank. if it is a fuel cap breather it should vent well.

Fuel lines can break down quickly esp if they are the wrong type of plastic and react to alcohol fuels.

Primer bulb vales do fail internally.

If it is hard to prime with the bulb you should replace that if you are confident your breathers are functioning. Your bulb should never look partially sucked in.

Prime with the fuel cap off....if it primes ok it is a venting problem.

Air locks in breather lines do not usually starve an engine from fuel.....it simply sucks that fuel back to the tank.

A kinked or pinched fuel line will also stop the engine quickly....check the line had not worked under something pinching it off.

If all the above fails check inside your tank that it has a mesh end on the pickup tube...if it does not there could be something in the tank blocking the pickup. 1 medium sized fish scale can really do your head in trying to diagnose it blocking the inlet and you can't see them in the fuel tank.....so if you really have the shits with someone....

[Noah Fitzpatrick]

i had a closer look this arvo, took the fitting on the motor side off and attempted to pump fuel but couldnt get any flow/fuel whatsoever (with a full tank as well). took the pickup out of the tank and the mesh on the end is still there with no holes. The primer bulb will push air out but then suck it back in?

[mangajack]

End of the fuel line when dsconnected will have a spring loaded ball to shut off the fuel flow when disconnected....you need to wedge it open to try the bulb.

If the bubl does not work I would presume it is faulty and jammed in the valve.

Easy test is to remove the bulb and blow back to the tank...if it blows back easy it will be the bulb.

[Noah Fitzpatrick]

yeah i took the fitting with the spring loaded ball off so just the hose was exposed to allow for fuel flow. no good. will try the bulb tmr. cheers for the advice

[Rigaz]

I always wondered how flickos magically worked out his outboard issues

[Noah Fitzpatrick]

aus fishing forums hit different 

 

[Ed.]

 I had a similar situation to what Angry51 said, the previous owner of my boat had fitted an additional filter to the fuel line as well as a bulb and the inner lining of the fuel line had separated and bunched up in front of the fittings, so it would let some fuel through but once you were going for a while at medium to high revs, it would eventually catch up and starve the motor of fuel, causing the motor to lose power intermittently.

 

[Noah Fitzpatrick]

checked fuel line and filter, no issues there. called up stones corner marine and they reckoned carby straight away. Wasnt too keen on the 5 week wait and the inevitable hit to the wallet though so went and got some carby cleaner, watched a few vids and took it apart. bit of cleaner in the jets and gallery, compressed air, and i chucked it back in. 

Was a very nervous first pull but she started straight away and ran sweet at idle for 15 mins or so, back on the water the next day.

[Angry51]

Time will tell if that fixed it but wouldn't have done any harm giving it a good clean Noah.

And saved a swag of money, let's know if the problems solved.

[Noah Fitzpatrick]

yeh that wouldve been it, little bit of water or grit in those jets is enough to stop fuel coming through apparently. Gave it a good run up a creek yesterday with no more issues.

[mangajack]

A word of caution, compressed air can ruin a carby by excessive force on some check valves and or force a clog further inside. When using compressed air blow across any opening, not straight into it.

Plenty of carbies have tiny wafer thin plastic check valves pushed deeply inside then you often can not see. Compressed air easily damages these and they are generally not replaceable.

Good to hear you got the engine running again....time will tell if it was the issue.

[Noah Fitzpatrick]

Lucky the big compressor wasn’t working then and I had to use the tiny one for blowing up mattresses I guess haha. Pretty simple little things in the small two strokes by the looks of it though? 

[Bretto77]

2 hours ago, Noah Fitzpatrick said:

Lucky the big compressor wasn’t working then and I had to use the tiny one for blowing up mattresses I guess haha. Pretty simple little things in the small two strokes by the looks of it though? 

You said early in the post that the primer bulb was sucked in??? The offender made it to the carby?

Anyway, happy days and happy boating

[Noah Fitzpatrick]

33 minutes ago, Bretto77 said:

You said early in the post that the primer bulb was sucked in??? The offender made it to the carby?

Anyway, happy days and happy boating

think that was a different issue with the connection to the tank that ive fixed up