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Ok, here is the story, last year i purchased a 26 foot c&c. It came with an outboard, nice Johnson 9.9 with an electric start. The motor worked just fine last year, on the last day of the pull out it died, and wouldnt start for a while. it did start later on that day, but would not rev higher and bog. Few days ago while on my boat, i put new spark plugs in, the old ones were black, completely black, i remember that last year they looked normal. I cleaned them up put them in, the motor started just fine, didn't shake anymore, didn't bog, etc... i ran the motor for half an hour, and after that it would start to bog. Removed the spark plugs and they were black again. check the fuel filter, checked the oil level, checked the cables on the spark plugs etc. All this was done with brand new fresh gas. Somebody suggested that the fuel line might be faulty and that it might be sucking in air. I tried a different one. I have removed the carburator, sprayed it throughout with carb cleaner etc.
obviously it is running to rich and the fuel is not burning up. Where to look? any adjustments on the carb? there isn't too many screws/adjustments on it.
The motor is 2002/2003 model. 9.9 Johnson with electric start. It is a four stroke motor.
Please help, or tell me where to look for the problem.
Any help is appreciated.
 

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Once known as Hartley18
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If the plugs are getting fouled I would not have thought it was sucking in air.

A couple of things: What condition is the tank in? Not full of grunge I hope?? Was the fuel filter clean? Is it using oil??

The idle mixture should normally be in the center position, but is easy to knock accidentally. What happens when you lean the idle mixture right out? Does the engine run smooth at idle or just conk out??
 

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I have a evinrude 9.9 (1996)... It kept happening to me until the motor seized...
I was told to check those:
Fuel line, fuel filter, carburator float, water pump...
Mine died before I get to the water pump...
If you have marine insurance called them up and let them know, some insurance companies cover user fault motor failures and the worst case scenario they will pay for the inspection/diagnostics of the motor...
Good luck...
 

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I'm not familiar with the Johnson 4 stroke models, but the older 2 stroke Johnson 9.9 motors have an ignition module that will go bad every few years from overheating. If the 4 stroke has such a module, check it out. All three of the Johnson 9.9 outboards I have worked on in the last three years had bad ignition modules. Good Luck!
 

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Black dry spark plugs on a four stroke are a sure sign of over fueling. There are only four reasons common to this. 1) Butterfly choke stuck on, or closing by itself, or in the case of a fuel enrichment choke, deteriorated "O" rings; 2)Float, needle and seat---flooded or fuel soaked float, dirt under the needle, damaged seat etc. and 3) main jet loose or missing, or laying in the bottom of the carb..4) if there is an air cleaner, a plugged or soaked air cleaner will cause the ventury vacuum to climb, sucking way more fuel through the jet.

Feetup.
 

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i have a 9.5 1966 jonhson seahorse i would like to know how to remove the fly wheel thank you. in order to get to the cellinod.
 

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Our 15/4 stroke is basically the same as yours. We've had our over 12 years and still running strong.
Low oil will cut throttle and gum up the plugs if run after light goes on, if light works. If oil level is OK, then circulation may not be (hense seized engine above).
Second; Is it at all possible you are running gas which someone has added oil? Throw away gas you have, clean carb and retry with straight gas.
Perhaps the timing belt needs replacement?
 
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