Rebuilt carb leaking gas all over

[Spare_Time]

1987 mercruiser 165 inline 4 (3.7 liter, the newer design of the old 470) with mercarb 2bbl carburetor.

I've been having one problem after the next. Refreshed the carb and set the float level to what the instructions said it should be and had the motor running ok. I Eventually figured out i had a bad fuel pump throwing all sorts of gas into the oil thus making the crankcase vapors a rich fuel blend. SO after just replacing the fuel pump i now go to start the motor and the carburetor is just dumping fuel all over. Down the venturi, out the top and around the base. I pulled the carb apart again and rechecked the float levels and needle valve for proper operation. All look ok to me. Put it back together and tried to run it with no luck.

I did one thing im hoping didn't screw anything up and that was adjust the accellerator pump pushrod. I set it to the level recommended in the manual. Could the be the problem? Any ideas? Am I best off just taking the carb to the marina and letting a mechanic rebuild it or is that a waste of $$$

anyone want to donate money to my boat? ha-ha! JUST KIDDING!!! (reference to a post earlier about some knuckle-head asking for money...i certainly feel his pain, but eventually I will get this running!!!!) Advise is mucho mucho appreciated


Thanks!!!!!
AL Conforti

 

[Maclin]

Re: Rebuilt carb leaking gas all over

I think you need to hand off the carb work to somebody else before you get strike three....

 

[a70eliminator]

Re: Rebuilt carb leaking gas all over

Probly a piece of grit worked loose when you replaced the pump and now it's hung up right on the needle seat, it's the only way the float bowls are going to fill to the point of overflow, so take it open again remove the floats and clean the needle and seat, blow it out with comp. air.

 

[Spare_Time]

Re: Rebuilt carb leaking gas all over

is there any kind of pressure regulator adjustment on the fuel pump? What is the fuel pump is putting out too much pressure from the factory? Too much pressure could certainly make the needle stay open and over fill....Is there a way to adjust they pressure?

 

[chiefalen]

Re: Rebuilt carb leaking gas all over

If it were my boat i would try one last time and rebuild the carb right. First the fuel filter in the fitting that goes in the carb is clean correct?

All the other filters are clean, correct?

Take the carb apart and soak it over night in carb cleaner. I use acetone.

Blow it dry with compressed air.

Now in the daylight check every hole. Clean? Seat clean? Ball bearing replaced?

The float holding air? Not full of fuel?

Put it back together. Now gently in with the adjusting screw gently. Out a turn and a half to start.

Fire it up and adjust from there.

If it doesn't work than new carb.

Some carbs can't be rebuilt.

Good luck

 

[cgrooves]

Re: Rebuilt carb leaking gas all over

I recently had a similar issue. I rebuilt the carb and set the float height / drop to spec. After re-assembly, the float would be 'stuck' in the down (needle valve open) position approx. 50% of the time when I would turn the carb upside down and blow air into the gas inlet connection. I took it back apart and verified the float height / drop was still set correct, verified that I used the proper thickness washer under the needle valve that was in there originally and put it back together. When I installed the carb on the motor and started it for the first time, the needle valve stayed open and gas rushed out like you describe. I turned off the motor and gave a good tap on the side of the carb with my adjustable wrench, which allowed the float to come up from its 'stuck' position and close the needle valve. Haven't had any more problems with it.

From what I've read on here, it seems to be a common problem that the float can 'hang up' when it is in the fully dropped position after a rebuild. During operation, the float obviously never reaches the fully dropped position on my carb, so I don't have to worry about that happening when there is fuel in the bowl. If you let all of the fuel out of the bowl (i.e. during a rebuild or perhaps even during your fuel pump change), the float will drop all the way down and can possibly get 'stuck' there. I used to put fuel in the bowl during re-assembly when I used to work on air-cooled VW's, and I'm thinking that if I would have done that during my recent rebuild on my boat carb that I wouldn't have had the problem described above.

Long story short......Tap on the side of the carb and see if it solves your problem (i.e. allows the 'stuck' float to rise up and shut off the needle valve).

 

[Maclin]

Re: Rebuilt carb leaking gas all over

For most carbs there are two settings for the float. One is the height which determines the fuel level in the bowl when running. The other is the drop down or lowest setting. The float hinging bracketing should have a tang that hits before the float drops all the way down. If the float drops down too far the needle can come out of the seat some and get cocked and jam. ALL of the parts have to be verified that all of their pieces are in order and are correct for the application. ALL of the measurements and settings have to be set or verified. If a person does not realize the significance of each piece of each part and the corresponding measurements and settings then they may take shortcuts. That is why I sometimes recommend to have someone else do the carb.

 

[cgrooves]

Re: Rebuilt carb leaking gas all over

For most carbs there are two settings for the float. One is the height which determines the fuel level in the bowl when running. The other is the drop down or lowest setting. The float hinging bracketing should have a tang that hits before the float drops all the way down. If the float drops down too far the needle can come out of the seat some and get cocked and jam. ALL of the parts have to be verified that all of their pieces are in order and are correct for the application. ALL of the measurements and settings have to be set or verified. If a person does not realize the significance of each piece of each part and the corresponding measurements and settings then they may take shortcuts. That is why I sometimes recommend to have someone else do the carb.

I understand fully what you are saying. However, I don't understand why I had the problem described above after my recent rebuild. The float height & drop were set dead on to spec. The washer under the needle valve was replaced with a washer of the exact thickness. Even though everything was set to exact spec, the float still dropped enough to allow the needle to get 'cocked & jam' after re-installation. Tapping on the side of the carb after the bowl filled with fuel allowed the float to come up and shut off the needle valve and I haven't had any problems with the carb since (the float obviously never drops all the way during normal operation). From browsing threads on this board, it appears that this is a common issue after a carb rebuild. I will add, that when I initially checked the float height / drop during disassembly, the height was right at spec but the drop was a little less than spec. Maybe a previous owner had run into this issue before and solved it by simply setting the drop a little less than what the spec says.

 

[Spare_Time]

Re: Rebuilt carb leaking gas all over

thanks for the replies. you folks are great!!!!

A few other things.... Can i get a replacement gasket for the top of the carb?
Im going to re-check the float and needle/seat. I checked the drop and float height three time to ensure I was accurate. Maybe something it in the seat fouling up the seal. On the other hand, I did soak the carb in carb cleaner for an hour. Im reluctant to strip the carb down again because the rebuild kit is $60....anywhere I can get the gaskets cheaper? I just need the gaskets, the new accelerator pump is well new....so is the power valve, check balls, etc....
if I soak the carb i'll need new gaskets....

where can I get just the gaskets?

Thanks!!!!