Mercruiser 4.3 - small fuel leak near fuel/water separator

sharktown · Feb 16, 2013

Hi there!

While changing my oil I found a small fuel leak at the place where the fuel line connects to the fuel/water separator.
It's not leaking around the thread, but its coming out between the bolt and the metal connector on the fuel line - see attached. Whats the best way to fix this? Is there a rubber seal where the fuel line connects? I havent taken the line off yet, but thats the next step.

Thanks for your help!

Don S · Feb 16, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

It's either the line or the fitting the line attaches to. Inspect and replace as necessary. No way can we do that inspection.

agallant80 · Feb 16, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Prob the seal. You can buy an o-ring kit for about $5 at many stores. I would try that first. If it still leaks I would look for a craked line. How small is the leek?

sharktown · Feb 16, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

ok - I will try to take it apart tomorrow. Hopefully it is just the seal. The leak is pretty small - the connector on the fuel line feels wet.

Fun Times · Feb 16, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Just so that you are aware, those fittings do not have any o'rings!

Grub54891 · Feb 17, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Fun Times said:
Just so that you are aware, those fittings do not have any o'rings!

Them are a double flare fitting,If they were over tightened in the past they will leak.Once the flair is crushed it cannot be snugged up and needs to be replaced.

sharktown · Feb 18, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Thanks everyone. Took the line off and both line and fitting look pretty clean. Waiting for my loctite 592 to show up before putting it back together. Any trick to getting a better seal? Anyone know what the torque specifications are? or just hand tighten and another 1/4 turn with the wrench?

I suppose if it still leaks after that, I will replace the fitting.
Not even sure where to start replacing the hose if that becomes necessary. It connects on the bottom of the engine and disappears into some box in a tight space right next to the motor mount.

Don S · Feb 18, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

You don't use thread sealer on flared fittings, you make sure there are no cracks, and it's clean and put it back together.
That sealer would be used on the fittings pipe threads where it screws into the filter housing.

ktbarrentine · Feb 18, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

That brass fitting didnt look the greatest (at least as far as I could see in the photo) and it doesn't take much (i.e. a fine scratch, debris, etc.) to cause a leak like you described. I would replace that fitting at a minimum...Just sayin'.

sharktown · Feb 26, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Cleaned up the fittings and put it back together with thread sealer. Replaced the filter and ran the motor for about 30 mins. Everything looks nice and dry now. Thanks everyone!

Grub54891 · Feb 27, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

So after you asked the questin,you used sealer against the advice here. Sometimes I wonder why people ask when they are gonna do what they want anyway. Hope that fitting don't leak while under way in the future,could be disasterous to you and your passengers.

sharktown · Feb 27, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Grub-Where in my post does it say I used the sealer on the flared fittings? I applied #592 Loctite Pipe Sealant to the threads of the brass fitting as recommended in the Mercruiser manual. And yes, I "hope that fitting don't leak" either - that's really why I came here in the first place.

Grub54891 · Feb 28, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Ok, sorry I misread it, I just get frustrated sometimes when people do things agaist what was recommended.
You should be fine! I've messed with a few flare fittings in my day with that sealer they put on and just overlooked the wording.
Happy boating!

sharktown · Mar 2, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Following up on this discussion, does anyone have any suggestions for gasoline fume detectors/alarms I can put on the boat?

Don S · Mar 2, 2013

Re: Mercruiser 4.3 - small fuel leak near fuel/water separator

Might want to post that question over in the Electrical, Electronics, Audio and Trolling Motors forum.

Then you get people looking at that question that own all types of boats, and not just reading a fuel leak question in the Mercruiser forum.

Mercruiser 4.3 - small fuel leak near fuel/water separator

Cadet

Honorary Moderator Emeritus

Commander

Cadet

Moderator

Vice Admiral

Cadet

Honorary Moderator Emeritus

Lieutenant

Cadet

Vice Admiral

Cadet

Vice Admiral

Cadet

Honorary Moderator Emeritus