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1990 25hp Johnson shutting down after a few seconds

nymcah

Member
I feel like I’ve tried everything with this motor... model #J25RLESB. It was running fine a few weeks ago. Tried to start it up last week and wouldn’t start. Noticed the primer on my hose was breaking down so replaced that. It’s got the manual pump-to-prime system, and I noticed a backup somewhere in there. Cleaned that out and replaced those hoses. There was some dark liquid spitting out of intake manifold into primer hose when I pulled rope... detached hose, turned engine over until all of it was gone.

Now, engine is very difficult to start but will get going with primer out. I’ve followed all the start-up procedures in the manual. Sprayed out the carb several times and made sure there are no cloggs. Carburetor bowl is filling up and primer bulb is firm. Spark is strong. When it does start, engine cuts out a few seconds after I push the primer back in. I’ve tried idle adjust screw.

Please help me!! I’ll try anything!! Open to any ideas.
 
I feel like I’ve tried everything with this motor... model #J25RLESB. It was running fine a few weeks ago. Tried to start it up last week and wouldn’t start. Noticed the primer on my hose was breaking down so replaced that. It’s got the manual pump-to-prime system, and I noticed a backup somewhere in there. Cleaned that out and replaced those hoses. There was some dark liquid spitting out of intake manifold into primer hose when I pulled rope... detached hose, turned engine over until all of it was gone.

Now, engine is very difficult to start but will get going with primer out. I’ve followed all the start-up procedures in the manual. Sprayed out the carb several times and made sure there are no cloggs. Carburetor bowl is filling up and primer bulb is firm. Spark is strong. When it does start, engine cuts out a few seconds after I push the primer back in. I’ve tried idle adjust screw.

Please help me!! I’ll try anything!! Open to any ideas.
Sounds to me like your slow speed circuit is clogged and with primer pulled out you are feeding it fuel then when pushing it in it cuts off any fuel and dies.I had a similar problem on my 20hp.Hard to start or no start and primer pulled out it would rev up or start then flood.I had even gone thru carb prior also,but it still had a small clog.Be maticculas and clean carb again.
 
Thanks for the help. I went through the entire carb again— soaked in carb cleaner for over an hour and blew out everything with compressed air. Still having the same issue.

I’m worried that there might be some water getting into the intake/cylinders. When I turn over the engine with the small primer hoses off, a dark liquid squirts out of the the intake manifold where the hose connects. Could this be water getting in somehow? Could pushing in the primer cause it to stop sucking out the water, causing the engine to shut off? Any help is very appreciated!
 
Thanks for the help. I went through the entire carb again— soaked in carb cleaner for over an hour and blew out everything with compressed air. Still having the same issue.

I’m worried that there might be some water getting into the intake/cylinders. When I turn over the engine with the small primer hoses off, a dark liquid squirts out of the the intake manifold where the hose connects. Could this be water getting in somehow? Could pushing in the primer cause it to stop sucking out the water, causing the engine to shut off? Any help is very appreciated!
Did you do a compression test? Could lead to a issue with head gasket.
 
Just tested compression... 90psi on bottom cylinder, 60psi on top. Top spark plug was very clean, bottom was dark. Does this suggest bad head gasket? Any other tests I should do before pulling it apart?
 
Just tested compression... 90psi on bottom cylinder, 60psi on top. Top spark plug was very clean, bottom was dark. Does this suggest bad head gasket? Any other tests I should do before pulling it apart?
Sounds like you should take the head off.This problem sounds like the same problem my brother was having on his older,but previously good running 9.9hp Evinrude.He asked me my input and he did compression check and had poor results.He ended up with bad head gasket and a faulty thermostat which may have caused a overheat condition which blew the head gasket partially.
 
Thanks so much Newyota. I’ll pull apart the head. Just ordered a new head gasket... is there anything else I should replace or check while I’m in there?
 
Thanks so much Newyota. I’ll pull apart the head. Just ordered a new head gasket... is there anything else I should replace or check while I’m in there?
Just curious how long you have owned this motor..Do you think it ever was over heated?
 
Very possible. Bought it from a guy not-running.
Thought you said it was running a few weeks ago?Did you have it running?Was it pumping water.Hopefully the pistons and cylinder walls are not ruined?No head gasket will fix that.Did you pull plugs and shine light in the cylinders?Might be able to see scoring?
 
Yes, that’s correct, sorry for the confusion. The guy I bought it from wasn’t sure if it would run or not as it had been sitting for a long time. Took it home and got it running, water coming out of telltale. Then tried to start it up a few weeks later and it wouldn’t start. Finally got it going but died after about 10-30 seconds.

Another thing- the first time I ran it I used a bucket. The time it wouldn’t start, I used muffs. The water pressure on my hose is very high. Is it possibly the muffs blew past a seal in the lower unit letting water into the cylinders?

thanks so much.
 
Yes, that’s correct, sorry for the confusion. The guy I bought it from wasn’t sure if it would run or not as it had been sitting for a long time. Took it home and got it running, water coming out of telltale. Then tried to start it up a few weeks later and it wouldn’t start. Finally got it going but died after about 10-30 seconds.

Another thing- the first time I ran it I used a bucket. The time it wouldn’t start, I used muffs. The water pressure on my hose is very high. Is it possibly the muffs blew past a seal in the lower unit letting water into the cylinders?

thanks so much.
No idea on the water pressure idea.Sorry.Did you check to make sure your spark was jumping a 7/16 air gap?The first thing the experts on here ask about the compression and the spark.But you definitely have a compression issue.Interested in the outcome.
 
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