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Old 13 June 2006, 07:31   #1
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Yamaha 30

Help.... Have just tried to run up our Yamaha 30hp outboard and we seem to have a bit of a problem with it. Firstly flat battery which has been fixed. Secondly once it runs it is very lumpy and inconsistent with its running. To start with it is OK but then after about 5 mins we lose almost all power and we have to struggle home on tick-over.

Engine hasnt been run much over the last year any suggestions??

Thanks in advance
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Old 13 June 2006, 10:27   #2
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have you opened the bleed valve on the tank? this can cause the loss of power after a few minutes as a vacuum builds up and only very little petrol can escape the tank. Sorry its obvious, but we've all done it!

The lumpy running could be lots of things if its been left standing, have you given it a quick service, including the plugs?

checked the loom for any corroded connections?(Particularly the supply to the coils).

Fuel filter blocked?

Nasher.
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Old 13 June 2006, 10:44   #3
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Hi Lozzer,

Could you describe the lumpy a bit more?
Lumpy as in jumping back and forth (I.e. One cylinder firing every now and then, not every stroke)
Does it produce black smoke at all? Have you checked to see if the choke might be stuck in the "On" position.

As Nasher said, the fuel vent is a very good place to start

Good luck!
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Old 13 June 2006, 11:26   #4
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thanks chaps will go and have a look in the next day or so.

The lumpy is more when you put the throttle fully down nothing happens except juddering, goes nowhere..... works fine for the first five mins but then it isnt interested. Checked spark plugs they looked clean, didnt have a filo guage so couldnt measure the gap but it looked right.

Exhaust is fine, water coolant all good. Filter looked clean but will check in more detail. I think it could be electrical as it doesnt want to fire properly.. Will check sparks better.

Anyhow thanks again and if you have any more ideas I would appreciate them.
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Old 13 June 2006, 12:01   #5
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My moneys on abit of crap blocking one of the carb jets, take the carb(s) off and blow through with compressed air, had a similar problem with an outboard of mine, turned out to be abit of bark clogging the fast jet.
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Old 13 June 2006, 12:36   #6
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Also the fuel will be as stale as heck! Unleaded starts to go off after six weeks. I'd ditch the old stuff and try running it on some fresh.
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Old 13 June 2006, 13:25   #7
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Like Alice says I would open the drain on the carb and pump some fuel through from a fresh tank before before taking anything apart .
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Old 13 June 2006, 13:59   #8
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Another thought from me, I dont know what type of ignition is on it, but the "newer" ones have a stator that controls the advance in timing if you increase RPM. It might be stuck in position or something.

Have you tried checking the bulb on the fuel line to see if it stays quite hard, or totally flat. Also, try pumping the bulb when it starts acting up, might have something to do with that, you can only try!
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Old 21 June 2006, 03:20   #9
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Thanks

Hi All that helped.

Thanks very much, managed to get the motor running after a couple of hours of tinkering.

Fresh fuel, new spark plugs, cleaned the carbs and she now seems to be running sweet (until the next time)

Anyhow thanks.
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