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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 16217
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a late 90's 25hp mercury that will run few minutes

Customer Question

I have a late 90's 25hp mercury that will run for a few minutes then shut down like it is out of fuel. I can squeeze the primer bulb and it will start again then same thing. I noticed that the bowl on the carb goes to about half empty when running. Is this normal or should it stay full? Any thoughts?
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.

Hi Dennis, my name is Jason.

Fuel is definitely not making it to the engine if you have to pump the bulb in order to keep it going.

This can be caused by a few things. The first and most common reason being a bad fuel pump. But before replacing it there are a couple of other things to check first.

The fuel pump is operated by crankcase pulses, if the engine has a blown piston it will not drive the fuel pump. This is actually very unlikely, but you would want to do a compression test first just to rule this out.

After that, if there is any kind of air leak in the system the fuel pump will draw air in through that leak instead of drawing fuel up from the tank. There are a couple of different ways to test for this by hooking up clear tubing and a vacuum gauge, but the easiest way is to simply prime the engine first. Then disconnect the fuel line from the pump. And then get a piece of scrap fuel line, and hook that up directly to the fuel pump, and then stick the other end right down into a gas can, and start the motor. If it now stays running, there is an air leak, and the pump is sucking air in. That filter cup will never stay complete full, when running, but if the o ring on that is leaking, the pump will suck air in instead of fuel up. If doing this makes no change, then the fuel pump is bad and needs to be changed out. Does that make sense?

I think that should do it. But I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

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Thank you

Expert:  Jason replied 1 year ago.

Hi Dennis, did that explanation all make sense to you? Do you have any further questions on the issue?

Expert:  Jason replied 1 year ago.

Hi, it looks like you read my answer and logged off without leaving a rating or a reply back. I do want to make sure I answer your question on the issue completely, and I think that I have. If you do have a further question on the issue please feel free to reply back. If not, the website has charged you to speak with me but they will not credit me for helping you out until you put through a rating for me. Please let me know if you are having trouble when trying to put through a rating.

Thanks again and happy boating!


Expert:  Jason replied 1 year ago.

Hi Dennis. Just checking in. Any progress?