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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10894
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 9.9 hp old motor its not getting a steady flow of

Customer Question

I have a 9.9 hp old motor its not getting a steady flow of gas to the carb. checked behind fuel pump and the engine is creating suction. I put a new fuel pump on it, it didn't look the same as the one that was on there. but the dealer says it was remanufactured. I bought a new gas tank and hose as I am new to outboard motors. can get the engine started but has to be on full choke to even run. any suggestions on what to do and steps I should take to find what the problem is would be greatly appreciated
Submitted: 2 years ago.
Category: Boat
Expert:  Tan replied 2 years ago.
Hello. My name is***** to use the choke to keep the engine running is a dirty carburetor. Then engine is starving for fuel. What is the make of your engine?
Customer: replied 2 years ago.
its a 1974 Johnson, I took the gas hose off the carb and it spits gas. like a squirt gun not a steady bead like a hose
Expert:  Tan replied 2 years ago.
That's normal at idle as the fuel pump works off the pulses of the piston going up and down. The fuel pump has to just keep a supply of fuel to the carb to keep the float bowl full of fuel. The fuel pump can deliver more fuel than the carb can ever use. So remove the carburetor disassemble, clean and install a carb kit. The engine is starving for fuel due to a dirty carburetor. The high speed jet is in the bottom of the carb which is where it will be clogged or partially clogged causing the issue you are having. The engine needing to be choked is the verification of a dirty carb. The tests we perform to determine a fuel related issue are choking to determine if carb is the issue and squeezing the primer bulb to determine if you have a fuel restriction from tank or fuel pump failure. Does this make sense? Do you need a source for the carb kit?
Customer: replied 2 years ago.
yes a source for a carb kit would be wonderful and how can I tell if its a primer bulb or tank. thanks this is starting to make sense and where do you think I could find an exploded picture of the engine to determine how to put the parts back together so I don't miss a step and make things worse
Expert:  Tan replied 2 years ago.
To determine if you have a fuel tank issue run the engine and squeeze the primer bulb if the engine runs better then you have a dirty fuel tank or a fuel line issue. If the tank is clean then replace the entire fuel line and primer bulb. Usually when the fuel line is hard or the primer bulb is hard they need to be replaced any way. Here is a video on the carb rebuild. Here is an exploded view of the carb. Here is a link to the carb kit. Post back if you need further assistance.
Customer: replied 2 years ago.
okay well I checked the carb.. spotless everything is spotless. we started with the choke on ran fairly well. then cut the choke off and it stalls, when my buddy pushed on the bulb I seen bubbles coming out of the fuel pump. don't know if that could be an issue. I guess the guy we got it from says its rarely ever been used he just let it sit in the garage winterized.
Expert:  Tan replied 2 years ago.
It's possible that's problem the pump shouldn't leak. This will allow air into the fuel and fuel starvation. These carburetors are very hard to get the idle circuits clean and if it still doesn't idle after replacing the fuel pump the carb has to be put in an ultrasonic carb cleaning tank to get it clean. These cars are very bad about this issue. The idle ports are so small that conventional carb cleaners don't work.
Customer: replied 2 years ago.
could I put something as a sealant on the outside of the pump to temporarily take care of the problem as I said earlier I just bought a new pump.
Expert:  Tan replied 2 years ago.
No it won't stick and it is on the outside of the pump. The pump produces pressure so it won't stay on the pump anyway.

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