Johnson Seahorse 25hp - no fuel

M

Michael L. C.

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Joined
Mar 17, 2002
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1
I need help with a 1981 Johnson 25hp motor which will not start by squirting gas in the carb, but it will start if you take out the plugs and put gas directly into the cylinder. I am new to outboards and don't know what avenue the fuel mixture takes to go from the carb on the front of the motor and makes its way back to the cylinder. This is my neighbor's motor and I am just trying to help him out. Please provide any information which will help us troubleshoot this problem. Thanks Mike
 
A

alcan

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Joined
Dec 14, 2001
Messages
2,505
Re: Johnson Seahorse 25hp - no fuel

Hello Michael <br />The two stroke engine needs two tpyes of compression to operate. Primary compression is the compression in the combustion chamber. Secondary compression is on the crank case. This crank case compression is what forces air\fuel mix into the combustion chamber. It sounds like you might have a bad crank shaft seal. I would test compression in the cylenders first. Then we can go from there.
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Johnson Seahorse 25hp - no fuel

Howdy Michael.<br /><br />As Alcan says, you need crankcase compression to pump mixture into the cylinder.<br /><br />Crankcase seals and reed valves seal the crankcase and allow this "scavenging" compression. A bad seal could cause your problem. Another possibility is a broken, chipped or bent reed valve.<br /><br />Good luck.<br /><br />Red sky at night. . .<br />JB :)
 
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