outboarrd consitenetly cutting out after starting and running?

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seumask

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Another Outboard question.
I have a fairly ancient Yamaha 8 that starts fine and idles normally to start with. However as soon as it's used for a couple of minutes it wont run at low revs, cutting out and will only then start with the throttle fully open if at all.
I have checked the fuel supply and made sure there is no water in the fuel by emptying the tank.
I have had the Carb off and appart none of the jets appeared blocked.

Does the considerable knowledge of the forum have any further suggestions as to what I might do to fix this issue. I suspect something more complex has gone wrong but don't know where to look?
 
I would suspect a blockage of the fuel filter attached to the fuel on/off tap; if your engine has that arrangement. I had identical symptoms on an engine and that was the cause.
 
seumask said:
Another Outboard question.
I have a fairly ancient Yamaha 8 that starts fine and idles normally to start with. However as soon as it's used for a couple of minutes it wont run at low revs, cutting out and will only then start with the throttle fully open if at all.
I have checked the fuel supply and made sure there is no water in the fuel by emptying the tank.
I have had the Carb off and appart none of the jets appeared blocked.

Does the considerable knowledge of the forum have any further suggestions as to what I might do to fix this issue. I suspect something more complex has gone wrong but don't know where to look?
Click to expand...
Really like to know more about the age / exact model but
Sounds like fuel flow problem. areas to look at ( again)
  • Float / float valve. ( if its a soft tip needle there should be a little spring clip linking the needle to the float arm)
  • Fuel pump
  • Fuel filter (inline between connector and fuel pump/ carb)
  • Fuel line and connector .... looking for air leaks including pick up from tank
  • Tank vent

Will it run / keep running if you keep squeezing the priming bulb?

Checked sparks and tried new plugs ?
 
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Sounds like a typical start of season case of gellified fuel blocking flow after a long period of no use.

Your symptoms match my problems of 2 years ago, the local outboard mechanic cleared the fuel blockage and described the fix as per the line above.
 
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parsifal said:
I would suspect a blockage of the fuel filter attached to the fuel on/off tap; if your engine has that arrangement. I had identical symptoms on an engine and that was the cause.
Click to expand...

It has remote tank hasn't it ?
 
Thanks for the advice so far. I have checked the bulb and while there was a small leak at the connection to the outboard I couldn't pump any more fuel in when the engine cut out. The carb bowl was full at this point. I'll replace the fuel connector anyway.
These symptoms were persistent at the end of last season and although I have not removed the carb this season it was left empty overwinter, I cleaned the carb several times before it was put away.

I was worried that it was a more deep set crankcase seal issue that only openend up when the engine had warmed up a little. BTW its not over heating
 
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If you are confident that you have definitely exhausted all possible fuel delivery problems then, perhaps it's time to check if the head gasket is blown or, worse still, the block is cracked :(
 
Gin said:
If you are confident that you have definitely exhausted all possible fuel delivery problems then, perhaps it's time to check if the head gasket is blown or, worse still, the block is cracked :(
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When it dies does it cut out abruptly, or just die away. If the former, then the problem is more likely to be electrics, if it dies away, then most likely cause is fuel starvation. Is the fuel tank air vent opening properly? Is the non return valve in the primer bulb functioning properly? Combined with an air leak this can kill an engine. The fact the engine will start with the throttle wide open suggests strongly there is a fuelling fault of some sort. What do the plugs look like after it has stopped? Are they dry and biscuit or whitish coloured, or are they wet and sooty? If the latter, it suggests possibly too MUCH fuel is getting to the engine and choking it off. Could be caused by the carb float too high, or not shutting off properly, etc. Is the choke lever actually connected to the choke plate - i.e is it lifting the choke plate or butterfly fully open when the lever is pushed? Some rely on a spring to hold them open when the choke is pushed in. If that sticks the engine is over choked and dies.
 
seumask said:
Thanks for the advice so far. I have checked the bulb and while there was a small leak at the connection to the outboard I couldn't pump any more fuel in when the engine cut out. The carb bowl was full at this point. I'll replace the fuel connector anyway.
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Are you sure the bowl is full, not just needle valve or float stuck?

These symptoms were persistent at the end of last season and although I have not removed the carb this season it was left empty overwinter, I cleaned the carb several times before it was put away.

I was worried that it was a more deep set crankcase seal issue that only openend up when the engine had warmed up a little. BTW its not over heating
Click to expand...

Anything is possible but if the crankcase seals were bad starting would be difficult.
 
Boathook said:
I had the same problems with a Yamaha Malta - filter in the fuel tap blocked.
Click to expand...

But I think you fill find that the OP's engine has a remote tank with an inline filter. He seems sure that the bowl is full of fuel anyway
 
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