View Full Version : carb leaking

05-11-2008, 04:36 PM
hi guys just had my boat in water for the first time since i rebuilt the holley 4160 carb,the engine started up after cranking for 10 to 15 seconds and it ran fine but i quickly noticed the carb was leaking heavily at idle .:mad:
i shut it down straight away but when i tried to restart it turned over but wouldnt fire .
the leak seems to be coming from underneath the diaphragm beside where the fuel pipe meets the carb and only leaks when the engine is turning (i cleaned it down and left standing with no leaks at all when it wasnt running)
any ideas would be great as i have removed the carb and gotta bring it to my mechanic tomorrow (auto guy not marine ):confused:


05-11-2008, 04:46 PM
My first thought would be float in front bowl is sticking.

05-12-2008, 02:38 PM
just been in with my mechanic his verdict is that the float is not sticking and there is no obvious sign of any leaks at all.....gonna have to tow boat back 40 miles now to investigate the problem thoroughly...

only happens when the sun is shining eh ..:rolleyes:

05-18-2008, 11:50 AM
hey rob935, what did you find the problem is, mine is doing the same thing, took it apart and can`t find anything wrong. lat me know

05-18-2008, 12:31 PM
Is it leaking where the fuel line enters the carb or just next to it? It is leaking only when running because the fuel pump is on and sending fuel to the carb. Can you give us a better idea of where the leak is coming from or give us a picture?

05-19-2008, 12:19 AM
well on mine it is leaking only when runnning, triple checked fuel inlet pipe not leaking from there drips coming from bottom of power valve. also not coming from pipe that joins the two fuel bowls. I took the front fuel bowl off and replaced power valve diafram. Needle and seat are not stuck but replaced it any way along with a new float. Just waiting until tuesday to get a carb to manifold gasket and star it up.

05-19-2008, 02:13 PM
hey guys , its not leaking from the fuel line or at the point it meets the carb but seems to be coming from beside that point under the diaphram or from the gasket just beyond it , and only leaks when engine is turning , mechanic has double checked the carb with no obvious answer so gonna bring the boat back to him on thursday and try running it then ,

will let you know the results .

thanks all.

05-20-2008, 06:52 AM
the problem area in the above picture is located in the bottom right corner to the left of the fuel intake underneath just around where the diafram is located ...

05-20-2008, 08:51 AM
Based upon your description of where it is, I think you are saying the leak is coming from the fuel pump cover assembly. It has the little lever attached to it that is activated by the throttle linkage. It only moves like a tenth of an inch, right? If this is the correct area, there are four screws around the pump assembly. You can remove the four screws and lift up the pump assembly and look at the diaphram to see if it is corroded or there are any cracks in the gasket or rubber piece (could occur from over tightening, did you replace this part when rebuilding the carb?). That could definitely cause the problem you are talkng about. At that point, you just have to buy a rebuild kit for it to replace that piece. The standard Holley Marine rebuild kit 703-47 comes with the replacement parts. I am not sure if Holley sells just the fuel pump assembly parts separate from a rebuild kit. Again, I am guessing based on your description where it is. Could you edit the picture with MS Paint and circle the area if I am wrong about where you are talking about?

Workin' 4 Toys
05-20-2008, 09:47 AM
Check your fuel level.
To adjust the fuel level you will need to take out the sight plug in the side of the fuel bowl and with it running Loosen the lock screw on top of the fuel bowl and turn the nut clockwise to lower the level or counter clockwise to bring up the level you want it to be at the bottom of the sight hole If you turned it too far down it might have bent the tang on the float. to get back to a starting place, you will need to take out the lock screw and turn the nut so the needle & seat is 1/2 way through the thickness of the nut then put the screw back in, then take the fuel bowl off and hold it upside down & level then bend the tang on the float so the float is level in the center of the fuel bowl. This will get you back to a starting place.

Workin' 4 Toys
05-20-2008, 09:49 AM

05-25-2008, 05:10 PM
hi rholmes ...in reply to your questions , you are right about the area in question being the fuel pump cover , the diaphram is brand new as are all the gaskets , needles , jets etc, and the leak seems to be coming from under the assembly but wont know for sure till i get it back to my guy tomorrow , hopefully will be something simple , thanks for th info .

05-25-2008, 07:41 PM
Sometimes wvwn new gaskets or the diaphram could have a leak. 1 out of every 1000 times, I know, but that could be it. Did you scrape the surface of the fuel pump cover to get off any old gasket material? If so, you could have accidently scored the surface. Hopefully your mechanic will have an answer.

05-25-2008, 08:21 PM
That pump as I understand shoots raw fuel in when you move the throttle a certain amount. You can buy it separately from Holley. I can't imagine it is more than $10 because it is included in a $30 rebuild kit. Try replacing. 4 little screws if I remember.

05-26-2008, 12:32 AM
That is the accelerator pump. It squirts a measured amount of fuel into the carb when you jump on the gas. This allows the revs to pick up prior to the main jets taking over basically. It is an often overlooked part of the carb and can be a big factor in common problems like bogging out of the hole etc. It is adjustable and should be adjusted in the carb was just redone. It's also a common spot for leaks. I would bet that the surface area was not clean when reassembled. I would remove it and clean in carefully and the reassemble. You can use a small amount of gasket maker if the problem is persistent.

Good luck. If you need to know how to adjust it let me know.


05-26-2008, 03:22 PM
thanks guys invaluable information as always, i know for sure that he had to scrape alot of old gasket material from the edges and may well have scored some of the surface area so would bet on that being a factor but will also look into the adjustment of the acc. pump...thanks again ,

05-26-2008, 11:18 PM
Mine is leaking too, but I havent even begun to diagnose yet too many other projects.... Here is something you may find helpful.


06-02-2008, 07:48 PM
hi guys figured out the problem to be the fuel line tube o ring , took 2 minutes to sort it out after diagnosis , always the simplest of things eh ??

thanks for all the help.

06-02-2008, 08:33 PM
Glad to hear it was that easy. You are right about the simple things.