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Author Topic:   gas leaking from carbs when boat is stored

wrecksnfx posted 03-14-2011 11:16 AM ET (US)
When walking past my boat in the driveway the other day I noticed the smell of gas. Upon inspection I noticed gas was leaking from the carbs(1996 90hp Evin.V4 Ocean Pro). I unscrewed the gas cap and a large amount of air rushed out like a tremendous amount of pressure had built up. I thought perhaps the vent in the cap wasn't working so I replaced it thinking the the pressure was forcing the gas through the carbs. But i noticed it again after replacing the gas cap. I took the boat out today and it ran fine at first but after a while the engine began to sputter like it wasn't getting gas and the rpms dropped. I checked the primer bulb and it was soft so I pumped it and the revs picked back up, would run for a bit then sputter and revs would drop again. Priming the bulb would fix the problem for a few minutes until it would repeat. The carbs were rebuilt with new carb kits just 2 months ago and the primer bulb has been replaced recently as well. can these two issues be related? any ideas what the issue(s) could be? thanks for the help
Tohsgib posted 03-14-2011 11:37 AM ET (US)
Either they are leaking real bad and causing a vacuum problem or your fuel pump went south.
pcrussell50 posted 03-14-2011 11:45 AM ET (US)
Somebody should correct me if I'm wrong, but if the fuel bulb is soft, but NOT collapsed, that sounds suggestive of an air leak associated with a failed check valve in the line or at the tank, such that the engine fuel pump is as likely to draw air as fuel. Tracing air leaks can be a crappy process, but suspect the easy stuff first... the line, fittings, and bulb. Checking fu lines on the motor is not fun. Other times, it is possible for fuel to not leave the and still have no air leaks. In that case, the fuel bulb will be sucked flat. I -think- that could be due to a failed check valve too. That certainly calls for repair/replace of the bulb and check valves.
-Peter
AZdave posted 03-14-2011 11:50 AM ET (US)
Was the outboard tilted up? My carbed V-6 outboards both spilled fuel when tilted, and I think it is routine for them to do so. The poor performance and collapsed priming bulb sounds like another issue. Probably it relates to an obstruction in the fuel line. This can destroy outboards. There is a lot of information on this site if you do a search.
Jeff posted 03-14-2011 12:52 PM ET (US)
What is happening is very common during this time of the year. As the air temps begin to rise the air in your tanks begins to expand. If you tank does not have an open event, or a two venting cap the expanding air in the tank forces fuel in the tank out what ever outlet it has, in this case a connected fuel line, this pressurizes the fuel line, forces fuel through the system and out of the carbs.
If your fuel tank has a twist open vent in the cap just leave it open. If you do not have a fuel tank cap that has a twist open vent on it, get one and leave that vent open.
pcrussell50 posted 03-14-2011 12:55 PM ET (US)
Good golly, what an ugly post by me. I was on my iPhone on a plane, trying to get out the post before they close the door and make you shut off your devices.
In short, if the bulb is collapsed, I'd suspect something wrong from the tank, venting. Excess pressure in the tank can fill, and then overfill, the carburetor float bowls. If the bulb is soft, (IOW full of air, not fuel), but not collapsed, engine fuel lines cannot be ruled out, either. If there is a Nick, Adlert, do I have that about right?
-Peter
Tohsgib posted 03-14-2011 02:06 PM ET (US)
Yes but the bulb was just changed...we all know that could still be wrong as well. I would remove cowl and squeeze the bulb while looking at carbs. If no leaks and bulb gets hard(don't squeeze the bejesus out of it) then it is your pump. Is the bulb facing the right way and basically pointing skyward? If not that is a major no-no as the check valve can't close. Is that a good bulb or a Wal-mart/West marine bulb? If not OEM then it could be junk even though it is new. If tank was not venting you would get a collapsed bulb, not one free of gas. This is actually real easy to diagnose if you kinda know your way around an outboard. My bet is on the pump but for what they cost I would double/triple check.
deepwater posted 03-14-2011 11:25 PM ET (US)
When you opened the tank by removing the cap there was allot of air that came out ,,The cap wasn't venting,,It lets air in (hard fuel bulb) and lets air out (no pressure no leaking carbs)

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Author	Topic: gas leaking from carbs when boat is stored
wrecksnfx	posted 03-14-2011 11:16 AM ET (US) When walking past my boat in the driveway the other day I noticed the smell of gas. Upon inspection I noticed gas was leaking from the carbs(1996 90hp Evin.V4 Ocean Pro). I unscrewed the gas cap and a large amount of air rushed out like a tremendous amount of pressure had built up. I thought perhaps the vent in the cap wasn't working so I replaced it thinking the the pressure was forcing the gas through the carbs. But i noticed it again after replacing the gas cap. I took the boat out today and it ran fine at first but after a while the engine began to sputter like it wasn't getting gas and the rpms dropped. I checked the primer bulb and it was soft so I pumped it and the revs picked back up, would run for a bit then sputter and revs would drop again. Priming the bulb would fix the problem for a few minutes until it would repeat. The carbs were rebuilt with new carb kits just 2 months ago and the primer bulb has been replaced recently as well. can these two issues be related? any ideas what the issue(s) could be? thanks for the help
Tohsgib	posted 03-14-2011 11:37 AM ET (US) Either they are leaking real bad and causing a vacuum problem or your fuel pump went south.
pcrussell50	posted 03-14-2011 11:45 AM ET (US) Somebody should correct me if I'm wrong, but if the fuel bulb is soft, but NOT collapsed, that sounds suggestive of an air leak associated with a failed check valve in the line or at the tank, such that the engine fuel pump is as likely to draw air as fuel. Tracing air leaks can be a crappy process, but suspect the easy stuff first... the line, fittings, and bulb. Checking fu lines on the motor is not fun. Other times, it is possible for fuel to not leave the and still have no air leaks. In that case, the fuel bulb will be sucked flat. I -think- that could be due to a failed check valve too. That certainly calls for repair/replace of the bulb and check valves. -Peter
AZdave	posted 03-14-2011 11:50 AM ET (US) Was the outboard tilted up? My carbed V-6 outboards both spilled fuel when tilted, and I think it is routine for them to do so. The poor performance and collapsed priming bulb sounds like another issue. Probably it relates to an obstruction in the fuel line. This can destroy outboards. There is a lot of information on this site if you do a search.
Jeff	posted 03-14-2011 12:52 PM ET (US) What is happening is very common during this time of the year. As the air temps begin to rise the air in your tanks begins to expand. If you tank does not have an open event, or a two venting cap the expanding air in the tank forces fuel in the tank out what ever outlet it has, in this case a connected fuel line, this pressurizes the fuel line, forces fuel through the system and out of the carbs. If your fuel tank has a twist open vent in the cap just leave it open. If you do not have a fuel tank cap that has a twist open vent on it, get one and leave that vent open.
pcrussell50	posted 03-14-2011 12:55 PM ET (US) Good golly, what an ugly post by me. I was on my iPhone on a plane, trying to get out the post before they close the door and make you shut off your devices. In short, if the bulb is collapsed, I'd suspect something wrong from the tank, venting. Excess pressure in the tank can fill, and then overfill, the carburetor float bowls. If the bulb is soft, (IOW full of air, not fuel), but not collapsed, engine fuel lines cannot be ruled out, either. If there is a Nick, Adlert, do I have that about right? -Peter
Tohsgib	posted 03-14-2011 02:06 PM ET (US) Yes but the bulb was just changed...we all know that could still be wrong as well. I would remove cowl and squeeze the bulb while looking at carbs. If no leaks and bulb gets hard(don't squeeze the bejesus out of it) then it is your pump. Is the bulb facing the right way and basically pointing skyward? If not that is a major no-no as the check valve can't close. Is that a good bulb or a Wal-mart/West marine bulb? If not OEM then it could be junk even though it is new. If tank was not venting you would get a collapsed bulb, not one free of gas. This is actually real easy to diagnose if you kinda know your way around an outboard. My bet is on the pump but for what they cost I would double/triple check.
deepwater	posted 03-14-2011 11:25 PM ET (US) When you opened the tank by removing the cap there was allot of air that came out ,,The cap wasn't venting,,It lets air in (hard fuel bulb) and lets air out (no pressure no leaking carbs)