50 hp 4 strke 2001 mercury carbs leaking out plunger rod, Please help,

bitsy4643

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Oct 26, 2009
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2001 50hp 4 stoke Mercury all carbs leaking gas out by plunger rod. Rubber bellows are deteriorated are gone. Would these prevent this leakage or they only there for debris protection? What would cause this gas leakage by plunger rods? Could ill adjusted floats cause this? Any help greatly appreciated. Thanks
 

Texasmark

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Dec 20, 2005
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Nobody jumped on this. What is a plunger rod? How about a couple of clear, well focused, pictures that might help in understanding your problem.
 

bitsy4643

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After 5 posting on various Mercury forums, and getting no reply, I have discovered that if you have to ask what a plunger rod is and the rubber bellows that go on it, you know nothing of Mercury, Tohatsu or Nissan carbs. These motors all take the same carb kit and these same carbs are used on many 9.9, 20, 30 hp motors. One local "certified" Mercury mechanic .had to look on computer to see what a plunger rod is. Another said he would rebuild carbs for 350 dollars but I must get an intake manifold gasket. This 50 4 stroke does not have a gasket only O rings . If anyone , novice or professional ever rebuilt this carb, you would not forget what a plunger rod is, the rubber bellows that go on it, and the function they serve.
Upon disassembly, for the "professional" mechanics and novices, the plunger rod, about 1 1/2 long by 3/32 D, is activated by throttle advance, goes through a brass fitting about 1/2d with 7/64 hole in center {very loose plunger rod fit and not sealed}. Rod goes to bottom of bowl to depress about 1/2 inch plunger that forces more fuel into carb. To my best assumption, the rubber bellows on rod at outside top of carb, serves to protect from debris and to protect from fuel linkage.
As someone who does not have great knowledge, it was inconceivable that no one answered this after all those postings. Maybe this will help someone else who may need an answer. Thanks for your forum.
 

flyingscott

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Apr 8, 2014
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Your plunger rod is called an accelerator pump. If you would have given that description people would have known what it was. No pictures did not help either, you also should have included the serial# of the motor.
 

GA_Boater

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49,038
After 5 posting on various Mercury forums, and getting no reply, I have discovered that if you have to ask what a plunger rod is and the rubber bellows that go on it, you know nothing of Mercury, Tohatsu or Nissan carbs. These motors all take the same carb kit and these same carbs are used on many 9.9, 20, 30 hp motors. One local "certified" Mercury mechanic .had to look on computer to see what a plunger rod is. Another said he would rebuild carbs for 350 dollars but I must get an intake manifold gasket. This 50 4 stroke does not have a gasket only O rings . If anyone , novice or professional ever rebuilt this carb, you would not forget what a plunger rod is, the rubber bellows that go on it, and the function they serve.
Upon disassembly, for the "professional" mechanics and novices, the plunger rod, about 1 1/2 long by 3/32 D, is activated by throttle advance, goes through a brass fitting about 1/2d with 7/64 hole in center {very loose plunger rod fit and not sealed**. Rod goes to bottom of bowl to depress about 1/2 inch plunger that forces more fuel into carb. To my best assumption, the rubber bellows on rod at outside top of carb, serves to protect from debris and to protect from fuel linkage.
As someone who does not have great knowledge, it was inconceivable that no one answered this after all those postings. Maybe this will help someone else who may need an answer. Thanks for your forum.

Why are you so impolite? Is this how you expect to get help? Please be considerate of those trying to help you. Thank you.
 

bitsy4643

Seaman Apprentice
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Oct 26, 2009
Messages
46
Plunger rod is a plunger rod, not an accelerator pump. All diagrams, parts, and descriptions describes as such. No mention ever of accelerator pump. It is not a pump but simply a rod with rubber bellows. If there is a pump, it is inserted in the body of the carb, that is activated by the rod... As I said before and will say again to all professional mechanics who could not answer my 5 posts on different forums with no reply after many days, you are not true mechanics or you could have answered this thread right away .Simply a poor excuse for certified mechanics that charge an arm and leg for services on engines are carbs to which they are not familiar. In my case, I am not or claim to be an expert, but I do possess common sense and know to describe things as they are. .Upon disassembly, parts lookup, carb rebuild searches on internet, I repeat, a novice, such as myself refuse to believe a plunger rod and the rubber bellows could ever be described as other than what they are.
 

racerone

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Dec 28, 2013
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I would say that no answers on 5 different forums means that there is someting about the way you are asking your questions.----No response is quite rare.--No response on 5 forums means even more I would say.
 

clanton

Rear Admiral
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Jul 9, 2001
Messages
4,876
Whatever you want to call it, the carbs will have to come off for a cleaning and float circuit inspection.
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
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49,038
Plunger rod is a plunger rod, not an accelerator pump. All diagrams, parts, and descriptions describes as such. No mention ever of accelerator pump. It is not a pump but simply a rod with rubber bellows. If there is a pump, it is inserted in the body of the carb, that is activated by the rod... As I said before and will say again to all professional mechanics who could not answer my 5 posts on different forums with no reply after many days, you are not true mechanics or you could have answered this thread right away .Simply a poor excuse for certified mechanics that charge an arm and leg for services on engines are carbs to which they are not familiar. In my case, I am not or claim to be an expert, but I do possess common sense and know to describe things as they are. .Upon disassembly, parts lookup, carb rebuild searches on internet, I repeat, a novice, such as myself refuse to believe a plunger rod and the rubber bellows could ever be described as other than what they are.

Again with the rudeness! These guys are trying to help you, but now I'm thinking you fixed it and want to show off your skills. Bravo!

What is the serial number of your Merc? This is always the first information required when working on Mercs - Every time!.

And say thanks to helping or trying to help every once in a while instead of calling us poor excuses for mechanics. Unlike the people quoting you repair prices, we work for FREE!

BTW - Your carb needs rebuilt, pure and simple. The accelerator pump is shot, allowing gas to leak past the pump and up the actuating rod and out through the torn bellows.
 
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