'96 Johnson 28 bogs under full throttle unless airflow is restricted by hand

R Alan

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Nov 13, 2011
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Starts fine. At low speed has intermittent cough. As throttle is increased, it picks up speed then at full throttle, bogs out badly. Found that holding hand over carb, limiting air, it runs fine...any ideas?

AJ
 
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EN2

Chief Petty Officer
Joined
Nov 19, 2007
Messages
404
Re: '96 Johnson 28 bogs under full throttle unless airflow is restricted by hand

It sounds like it is running lean,when you put your hand over it the mixture richens up. Take your carb apart and give it a good cleaning , high speed jet .
 

R Alan

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Nov 13, 2011
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Re: '96 Johnson 28 bogs under full throttle unless airflow is restricted by hand

Thanks for the input. It it possible the mix richens because there too much air? Could there be an air leak? Where might that be?

AJ
 

losnbama

Petty Officer 2nd Class
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Jul 31, 2011
Messages
154
Re: '96 Johnson 28 bogs under full throttle unless airflow is restricted by hand

anywhere there is a gasket,hose(clamp) etc is potential for a leak
 

R Alan

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Nov 13, 2011
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Re: '96 Johnson 28 bogs under full throttle unless airflow is restricted by hand

Thanks again...so you agree, it could be an air leak that is causing the lean mix? I am asking because if it were a fuel clog in the HS jet or elsewhere, why/how would the motor rev up high enough to plane the boat when air is withheld? Seems like its ability to do that rules out fuel starvation...
 

losnbama

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Jul 31, 2011
Messages
154
Re: '96 Johnson 28 bogs under full throttle unless airflow is restricted by hand

or could possibly be a bad membrane in the fuel pump,not being able to pump more fuel at higher rpm's. i would check the pump as well as clean the carb. u can check the pump by routing the out to carb bowl line into a clear container and turning over the motor and see how its pumping.there should be a solid pulse of fuel each time you pull it over.if it pumps good here it should do.btw holding yur hand over the carb is basically chocking the motor,a sure sign of a fuel delivery problem...
 
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