1972 johnson wont start after it warms up

mtitan

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just got this motor 1972 25 hp johnson starts great cold runs great for a long run but is hard as crap to start after long run and no cool down time, can anyone help please.
 

ADK_Boater

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Re: 1972 johnson wont start after it warms up

Are you choking it while trying to start it when it's warm, if so that may be the reason it is hard to start.
 

boobie

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Re: 1972 johnson wont start after it warms up

Check your spark when this happens. Should jump a 7/16 " open air gap.
 

Daviet

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Re: 1972 johnson wont start after it warms up

Might also check to see if gas is puddling in the carb throat.
 

mtitan

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Re: 1972 johnson wont start after it warms up

Might also check to see if gas is puddling in the carb throat.

not chocking it to restart. havent check spark yet was on water both times it happened and i aint got a clue what puddling in the carb throat is are how to check it.
 

mtitan

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Re: 1972 johnson wont start after it warms up

not chocking it to restart. havent check spark yet was on water both times it happened and i aint got a clue what puddling in the carb throat is are how to check it.
oh yea it will backfire while i am trying to restart it
 

Daviet

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Re: 1972 johnson wont start after it warms up

Look in the carb when you shut it off and see if you can see gas laying in the carb throat.
 

boobie

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Re: 1972 johnson wont start after it warms up

If it's back fireing it still sounds like an ignition prob.
 

mtitan

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Re: 1972 johnson wont start after it warms up

If it's back fireing it still sounds like an ignition prob.
okay went out yesterday did it again when i got home i relized both spark plugs were real loose, guess my son forgot to tighten them so i think that might be the problem, what ya think
 

mtitan

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Re: 1972 johnson wont start after it warms up

ok, thats not it. let me ask yall this, if it is the coils which one could it be, the coil under fly wheel or the ones next to spark plugs.. and if its not cracked how to tell which ones over heating and messing up. thank yall a alot, I am glad i found this web site. yall are a bigggggggggg help.
 

AlTn

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Re: 1972 johnson wont start after it warms up

when hot and no spark at either plug...if this is a coil problem it's most likely the one under the flywheel as it's unlikely both external coils would fail at the same time...if one plug has a spark, most likely the charge coil < under the flywheel > is good and the coil producing the spark is good, the other coil is suspect...all this is contingent on this being a loss of spark problem..you could be losing compression when it's hot or the fuel pump diaphram is weak or possibly losing crankcase vacuum when it gets hot...start with the spark check tho'
 

boobie

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Re: 1972 johnson wont start after it warms up

You may want to post the correct model # ???
 

mtitan

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Re: 1972 johnson wont start after it warms up

can not find anything on this motor with model or serial number. no plate or plug on motor ....nothing. that another problem. going to get pictures on here soon but after looking at diagrams of parts on marineengine.com i am pretty sure its a 1974 now.
 
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