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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10897
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 1972 Evenrude 18hp outboard. When I pump the ball,

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I have a 1972 Evenrude 18hp outboard. When I pump the ball, gas comes out the 1/4 inch hole on carburator. Ball get soft very often.
Hi, The carburetor need to come off and be disassembled, cleaned and install a carb kit. The fuel coming out the vent hole is the inlet needle not seating properly and allowing the fuel to over flow. The primer bulb will get soft carb won't hold pressure. When running the motor, the bulb doesn't fill with fuel fuel only passes through the bulb therefore will be soft when running.
Customer: replied 6 years ago.
I did as described in the "answer." The needle valve and seat were replaced. New gaskets installed. Motor operates very well at full throttle. When trolling or idling ball gets soft repeatedly.
Does the engine pick up rpm's when you squeeze the primer bulb? The bulb doesn't stay hard when running the fuel is only flowing thru, there is no pump to keep the ball hard. You can unseat the inlet needle if you squeeze the primer bulb hard enough. This will cause the carb to over flow out the vent..

Edited by Tan Partin on 7/28/2010 at 8:17 PM EST
Customer: replied 6 years ago.
Yes. The engine nearly stalls. That's how we know to fill the ball. The engine then resumes the rpm as before.
Your fuel pump is failing. When you squeeze the primer bulb you are doing the same as the fuel pump making pressure.Diagram of  Evinrude Parts 1972 18202R 1972 FUEL PUMP Diagram p/n(NNN) NNN-NNNN
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