Carb float height

R

RyanB11

Cadet
Joined
Jun 1, 2010
Messages
9
Quick question for you carb gurus. I have a 1996 J 40 hp. If the float height is set too high, Would that allow for too much gas and cause a rough idle? My motor runs fine at 1500 rpm and higher but idles very rough. After rebuilding both carbs I am second guessing every step I've done. I know that I have carb issues because after the 3rd time of rebuilding them I did not fully tighten the bottom drain screw. After running a mile or so up river it let go and my rpms dropped. I pulled the cowling off and noticed gas coming out of my drain screw. However, She was idling perfectly at 800. So my goof actually might have gotten me closer to my problem. Rookie move I know, but nonetheless a learning experience. Come on fellas, Help me out here. Gotta get some fish in the cooler. Ryan.
 
M

milmat1

Petty Officer 2nd Class
Joined
Apr 29, 2010
Messages
137
Re: Carb float height

I don't know your Carb. But in General YES the float height will certainly effect the mixture. Also since it runs good when the throttle is open maybe the seat isn't sealing off the fuel at all.?? Just a Thought.. Are there any signs of fuel spilling out from the carb bowl..?
 
R

RyanB11

Cadet
Joined
Jun 1, 2010
Messages
9
Re: Carb float height

No sign of any leaks, I may have not adjusted the float correctly. Also if I pump the bulb it shhos out of the carbs. Will the needle block this as well?
 
bkwapisz

bkwapisz

Chief Petty Officer
Joined
Oct 20, 2009
Messages
441
Re: Carb float height

IF the needle and seat checked out ok, then the float is adjusted incorrectly as there is too much fuel at idle causing an over-rich condition. That is why when you opened the drain plug it idled well, because it wasn't flooding from that carb any more.

And no, when you squeeze the bulb there should not be fuel flooding out of the carb.
 
jtexas

jtexas

Fleet Admiral
Joined
Oct 13, 2003
Messages
8,646
Re: Carb float height

Yes, gas should NOT be coming out your carbs. Ever. (ok the occasional droplet while the engine's running).

It's running rich (more gas less air), you just don't notice it at high RPMs.

Hold the carb upside down (bowl removed). the float should hang exactly parallel with the carb body. Adjust by bending the tang ever so slightly.

Oh, and sometimes this is the result of forgetting the valve seat o-ring.
 
R

RyanB11

Cadet
Joined
Jun 1, 2010
Messages
9
Re: Carb float height

Alright, going to adjust the float height tomorrow. Will a correctly adjusted float stop gas from flooding out the top of the carb? Or is that a seperate issue?
 
jtexas

jtexas

Fleet Admiral
Joined
Oct 13, 2003
Messages
8,646
Re: Carb float height

RyanB11 said:
Alright, going to adjust the float height tomorrow. Will a correctly adjusted float stop gas from flooding out the top of the carb? Or is that a seperate issue?
Click to expand...

Assuming the needle and seat are not worn out, and the seat is firmly installed with its o-ring in place, I believe correcting the float height will stop your leak.
 
trailshredder

trailshredder

Petty Officer 1st Class
Joined
Apr 25, 2011
Messages
283
Re: Carb float height

RyanB11 said:
Quick question for you carb gurus. I have a 1996 J 40 hp. If the float height is set too high, Would that allow for too much gas and cause a rough idle? My motor runs fine at 1500 rpm and higher but idles very rough. After rebuilding both carbs I am second guessing every step I've done. I know that I have carb issues because after the 3rd time of rebuilding them I did not fully tighten the bottom drain screw. After running a mile or so up river it let go and my rpms dropped. I pulled the cowling off and noticed gas coming out of my drain screw. However, She was idling perfectly at 800. So my goof actually might have gotten me closer to my problem. Rookie move I know, but nonetheless a learning experience. Come on fellas, Help me out here. Gotta get some fish in the cooler. Ryan.
Click to expand...

Having a similar issue and wondering if your float adjustment resolved your issue?
 
R

Rick.

Captain
Joined
Jul 30, 2006
Messages
3,740
Re: Carb float height

I have a 1995-40HP Johnson. The initial slow speed needle setting is out 2 1/2 turns (says OMC service manual). Best of luck. Rick.
 
patrick4266

patrick4266

Chief Petty Officer
Joined
Nov 29, 2007
Messages
591
Re: Carb float height

Gas should not squirt out when you pump the bulb. Set the level at just slightly below level not above.
 
You must log in or register to reply here.
Top