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carb problem

Customer Question
carb problem
Submitted: 8 years ago.Category: Boat
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Answered in 2 minutes by:
6/14/2010
Marine Mechanic: Jason, Boat and Mechanical Expert replied 8 years ago
Jason
Jason, Boat and Mechanical Expert
Category: Boat
Satisfied Customers: 210
Experience: 10 yrs. running and working at my boat dealership.
Verified
What exactly is going on, and what is the question you would like answered?
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Customer reply replied 8 years ago
engine is erratic sometimes it runs up on plain fine other times it bogs down cannot get it up on plain, other times runs down the river half throttle with no problem then you accelarate to full throttle it will run fine for a time then just dies right out and is almost impossible to get back up on plain. Other times she idles perfect and times you can not keep it idling without it just quiting.
but it usually starts right back up. Had the carb off and replaced the acellarator pump and makes no change in the way it runs. HELP My name is Jon
Marine Mechanic: Jason, Boat and Mechanical Expert replied 8 years ago
Jon, I am going to be logging off, and am going to opt out to allow other experts the opportunity to get right with you. At least now we know what is going on. Thanks for the description. Have a good night.
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Marine Mechanic: Jeff G., Marine Mechanic replied 8 years ago
Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4,730
Experience: 42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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Welcome,
I will be happy to assist you. If you have a question or need clarification please post back at any time.
It is sounding like you are not getting proper fuel flow. First thing to check is the fuel pump pressure. Make sure you have adequate fuel flow. If you do check the carb.
When the engine does not want to accelerate or bogs down squirt a little gas into the carb. I use a trigger type small oil can for this. If the engine picks up the problem is in the carb. If not we need to look elsewhere. You could have a weak fuel pump, trash in the carb, inlet needle sticking etc. A total cleaning and adjustment would be a good idea. Particularly look for corrosion in the bottom of the float bowl or any contaminates such as water.
Change out your water separator if equipped.
Jeff
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Customer reply replied 8 years ago
Hi Jeff,
you are saying if I squirt gas into the carb when it bogs down and the engine picks back up then that isolates the problem to the carb. We have had the carb off and apart and replaced the accelarator pump by my auto tech. Not sure which way to go know. My auto tech is very capable but not an expert on marine. Help, Jon
Marine Mechanic: Jeff G., Marine Mechanic replied 8 years ago
Your engine is not that different from auto with the exception cars haven't used carbs for over 20 years!
If he only replaced the accelerator pump and didn't do a through cleaning the that could be where the problem is. If the throttle is not moved, such as while cruising, the accelerator pump isn't being used so it would have no bearing on the engine dying. If when you go to accelerate you don't have enough fuel in the carb then the accelerator pump wouldn't work very well. So we need to look at fuel delivery and the carb itself.
Squirting a little gas into the carb will do the same as the acceleration pump. So if the pump can't put any fuel through the squirt can will.
Jeff
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Customer reply replied 8 years ago
Jeff,
When I pump the throttle it picks back up briefly and then falls back off.
Jon
Marine Mechanic: Jeff G., Marine Mechanic replied 8 years ago
When you are pumping the throttle you are squirting fuel into the intake. So that is telling me you either have a fuel delivery problem, restricted fuel or fuel pump or a carb problem, not letting enough fuel in and basically the carb is running out of fuel.
Fuel pump test
Vacuum test the fuel lines, look for a restriction.
Do a total rebuild of the carb
Jeff
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Customer reply replied 8 years ago
Hi Jeff,
Yesterday I put the boat in the water. Fired it up it idled great. threw it up on plain, ran it about half throttle or more for about five miles did not miss a beat. Then drop the throttle, in about half a mile it falls on its face and almost impossible to get back up on plain ,idles fine and goes along at idle speed fine at this point. Pull it back out, thinking there is something in the gas. I get the tank drained put fresh gas in tank. Put the boat back in the water and will not even idle smooth or can't get it up on plain. just so erratic, which direction would you go first.
Jon
Marine Mechanic: Jeff G., Marine Mechanic replied 8 years ago
I would go through the carb and do a fuel pump test.
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Customer reply replied 8 years ago
Jeff,
How do you do a fuel pump test.
Jon
Marine Mechanic: Jeff G., Marine Mechanic replied 8 years ago
A fuel pump test is done with a fuel pressure gauge inline between the carb and the fuel pump. Your car friend should have the tester, you may be able to rent one at an auto parts or you can buy one from an auto parts or Sears and the adapter from Mercruiser.
Start the engine and run it at idle and then about 2500 rpm. Take pressure readings and give me the results. This will tell you the carb is getting enough fuel.
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Customer reply replied 8 years ago
Hi Jeff,
I have to go out of town for a day I will be back in touch soon, thankyou, Jon
Marine Mechanic: Jeff G., Marine Mechanic replied 8 years ago
Just let me know how it goes.
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