200 efi xri - Fuel smell in bilge

[Too fat 2 fish]

Got a 94 Merc 200 efi xri motor on a 94 Astro hull. Have owned boat about 3 years and always has strong fuel smell in bilge, even after sitting a while. Also gets a sooty buildup inside bilge. I'm fairly positive I don't have a fuel leak and bilge is always bone dry.

Have recently replaced plugs, primer, oil check valve and all fuel lines. Thanks in advance for any help

s/n is 06145588

[Rip Bass]

If you smell fuel and have sludge in the bilge then I’d say you do have a fuel leak somewhere. Gas will mix with water and make sludge. Can you access the tanks to see all the fittings on top? Might be a dried out or cracked hose there or a bad gasket on the sending unit. I think it’s worth checking,gas fumes plus a spark equals BOOM.

[Too fat 2 fish]

Thanks for the reply. I should have said soot rather than sludge. Bilge stays bone dry. It's almost like the exhaust is being blown back in. I can only get to one fitting on tank, where fuel line attaches. Has a vented fuel cap, could that cause this?

[OldTimer57]

any leak could cause this. You should not have "soot" in there, as that is a by-product of combustion. Combustion in the bilge would be a very bad thing. Gas fumes plus moisture might produce something that looks like soot, but it should be more gummy than powdery. That's an old boat, made way before E10 came along. You should check the FAQ here and make sure your in-boat fuel system is up to E10 specs, fuel line INSIDE and OUTSIDE the tank, plus the primer bulb and such.

[Rip Bass]

Those old vented caps have a separate vent line that connects to the fill pipe just under the cap,you might smell fuel there at times but not in the bilge from there.Is there any way to run a clean white cloth over the top of the tank? Even if you have to use a stick or something to reach. If you can see the top of the tank you can soak the area with soapy water and put about 5psi of air in the tank through the fill cap,if you see bubbles then you have a leak.
Oldtimer,he says he has recently replaced the fuel lines and it sounds like the problem occurred before that.

[JOE54]

should be no fuel smell , check pulse hose from mtr to remote tank for cracks

[Rip Bass]

Joe54,are you talking about the fuel line or the oil line? I’m thinking there is a single hose to the fuel tank so that pulse hose has me puzzled.

[leonreno]

I believe he is talking about from crankcase to oil tank, it could leak exhaust or fuel gases if leaking in the boat.

[JOE54]

^^^^^^ yep

[Too fat 2 fish]

Joe - Hose leak between crankcase and oil tank seems like a good possibility. I'll check that out

Rip Bass - I can see top of tank pretty well I guess. I understand the soapy water test with air pressure but what am I looking for with the white cloth?

[Rip Bass]

Just to see if you could wipe up or see any fuel on the cloth. Might be puddled on top of the tank.

[lpugh]

Check the filler neck closley while filling the tank, very common leak point on older boats

[JOE54]

+1^^^^^^

[EuropeanAM]

Fuel cap and vent mounted outside the bildge area correct?

[Too fat 2 fish]

Fuel cap and vent mounted outside the bildge area correct?

Yes. Vented cap mounted on gunwale

[EuropeanAM]

May need to inspect the fittings on the tank itself, and don't overlook the FUEL SENDING UNIT GASKET.

Above all- consider this a SAFETY CONCERN- Leaking Fuel or Vapors carry with them a risk of FIRE or EXPLOSION. I would not recommend operating the boat until you locate and correct this leak.

[Too fat 2 fish]

Thanks for all the help. Filler tube was slightly cracked on tank end. Would leak while filling and (I assume) when fuel splashed around in tank.

[JOE54]