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9.9 Mariner maybe 1994 ser # 0G004648

T

tonysworld

New member
This motor is running rough with a cough or sputter at WOT and at idle.. I have replaced plugs, rebuilt carb, fuel pump etc. I checked both cylinders for fire and both are working fine. Today I pulled reed valves off and there is a very small light leak thru 2 of the reeds where they close to body of valve. This motor does not seem to run at high enough rpm, but I have ordered a tach to verify. It was running great at beginning of season, but has gradually goten less power in last 3 months. It is on a 24 foot pontoon. The sputter is like popcorn popping with a nice little burst of smoke when it pops. Also, the smell of fuel is extremely strong around the motor. I can only find 1 adjustment screw on carb and have set it as I have found explained on internet/\. A manual has been orderedm but in the meantime, what should I be checking? I will order new reed valves tomorrow. However, I don't truly believe this is my primary problem. Thanks.
 
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guyjg said:
Have you checked compression? Try turning the idle mixture screw CCW 1/2 turn.
Click to expand...

This is my plan for today, I am unsure what good compression should be, whiich is why I ordered a manual. I'm hoping both will be close. As far as ther idle mixture screw, I cannot find any good images on the internet. The only adjustment screws I can find is 1 at the top of the throat opening on the front of the carb and another on the side that operates the butterfly opening and will raise or lower opening. I am assuming the 1 you are referring to is the 1 on the front. Thank you for your suggestions.
 
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Even if the idle mixture screw (top front of carb) is not adjusted properly, that would not make it do what's happening at WOT. You need to do a plug test to see what's happening: Run it WOT for several mintes, then shut it right down--no idling time. Then pull plugs and read their color.

I'll bet they're stark white (meaning lean operation--not good!)

Do that and get back to us.

Jeff
 
fastjeff said:
Even if the idle mixture screw (top front of carb) is not adjusted properly, that would not make it do what's happening at WOT. You need to do a plug test to see what's happening: Run it WOT for several mintes, then shut it right down--no idling time. Then pull plugs and read their color.

I'll bet they're stark white (meaning lean operation--not good!)

Do that and get back to us.

Jeff
Click to expand...

I tried this and the plugs were a perfecy brownish tan color, however, I did get the manual and followed the directions for the idle mixture screw. I turned it out and out with no change and if it turned it all the way in it would bog down. I then backed the screw all the way out of the carb and held in my hand while it was running and there was no change yet again. I am convinced that there is some sort of obstruction. I am pulling the tank topmorrow and thoroughly cleaning and draining it. I will replace the fuel line and primer bulb, but most importantly, I am bringing in an expert to observe the actions before proceeding any further. Hope to have it all resolved tomorrow evening. Once again, thank you for the help.
 
I then backed the screw all the way out of the carb and held in my hand while it was running and there was no change yet again.
Click to expand...
The carb is dirty...it needs a GREAT soak and cleaning!
 
I do believe this is the problem. When I rebuilt it I soiaked it in a can of carb cleaner with the basket. I did not do any probing or scrubbing as it was my first time doing a boat carb, but I figured there wasn't much difference in this and my motorcycle (4Stroke), I'm obviously wrong with this assumption. The lake I dock on appears to have a lot of issues with their fuel, so I had just order a flo n go tank to take to my dock, but this is after using their fuel all year. Once again, Thanks.
 
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