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77 Johnson35hp stalls at full throttle after 20 seconds

A

apj

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"Guys, tried everything?..
Mo

"Guys, tried everything?..
Motor was perfect for 2 years use...
Symptom is.. Starts and idles a treat, runs clean at half throttle in 5 min test.
Give it full throttle and it runs clean for 20 seconds then dies.. dead, starts with 3 pulls and goes at full throttle for another 20 seconds.(not missing or spluttering - clean death)
checked line and tank, tried with cap loose, no leaks in lines, tried bypassing bulb, stripped and cleaned carb -looked fine anyway, bulb looks fine, seat ok and not leaking, filter clean,tried a loaner pump (although was from a 9.9hp johnson) but did exactly the same.
Emptied tank/new fuel/mix..
How can I test/verify what the cause is?
I'm sure it's fuel, not electrical.. just feels fuelish (if that's a word).. annoying cause I can only test it in the water under load which means.. you guessed it - whinging kids. Would like to fix myself so any tricks in how I can narrow down the culprit would be appreciated.
thanks
AJ"
 
"Connect the tank hose straigh

"Connect the tank hose straight to the carb and use the bulb as pump.
If everything ok, it narrows down to fuel pump or quick connector seals (0-rings)"
 
You use the term " clean d

You use the term " clean death " ----To me that is an electrical / ignition issue.Look for broken wire on the magplate.Hook up a timing light to see if " ignition fails after 20 seconds.
 
"Will try both suggestions and

"Will try both suggestions and report back, thanks guys.
I did suspect electrics at first, but it runs too nice, no missing and runs neat at slower speed.. stripped all electrics back and cleaned up magneto/pickup.. cleaned all connectors and checked/re-insulated all wires in the process.. all looked spotless.. will test for failing ignition but."
 
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