2008 yamaha 4 stroke outboard

garyreece

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Mar 30, 2011
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3
I was going down the lake wide open and motor spit back violently. The kill switch was failing I later found.But now I hear a tapping coming from engine. I know this will be bad, but has anyone ever heard or had this happen. The tapping is at the piston area. 30 dollar kill switch probably killed it.
 

99yam40

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Sep 7, 2008
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tell me how a kill switch would break a motor?

Not sure on the 4 strokes but 2 stroke it killed spark
 

garyreece

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Mar 30, 2011
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When loading boat, motor seemed to be bogging down going on trailer and spit again and cut off, but not at high speed. Is this unrelated? I just know that after violent cut off , it started the tapping.
 

99yam40

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Sep 7, 2008
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the spit you speak of could be a lean sneeze.
could have popped a fuel pump diaphragm when it over pressured the crankcase.
Tapping noise I am not sure of,
maybe you were running lean and popped a piston.
Compression test of leak down will tell if all cylinders are sealing properly

Oh yea, if the flywheel tried to change direction quickly or stop when it sneezed it could have sheared the key on flywheel.
 
Last edited:

Silvertip

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Sep 22, 2003
Messages
28,758
With the kill switch pulsing the ignition, the timing belt could have jumped a cog and a valve(s) momentarily contacted a piston. Yes -- this is NOT a good situation. Overhead cam outboard engines are generally interference engines -- meaning if valve timing is off, piston-to-valve contact occurs.
 

Capt Ken

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Jul 30, 2002
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2,269
Is it a F15 or F300? Hard to answer a question without identifying the engine.
 
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