fuel smell

[Lee75]

I had my 3100SE out yesterday and whilst cruising up the river at 8 knots i kept getting a smell of fuel, i would then turn on the blower and it would stop but then come back 10-15 minutes later, Im new to boating so was wondering if its normal at low speed or should you never be able to smell any fumes at all?

[Phillbo]

Fuel smells on a boat are bad juju.... Find the source and fix it...

What kind of engines? Year?

[Lee75]

Hey mate, its a 2006 with 5.0 mercruisers

[mmwjr]

Do you only smell gas when the engines are running? If not either a fuel line or the tanks is leaking. If only when running try running one engine at a time to see which one is causing it.

[Lee75]

ive never noticed the smell when its not running, but ill try running one at a time,

[mmwjr]

Originally Posted by Lee75

ive never noticed the smell when its not running, but ill try running one at a time,

Then it’s probably not the fuel tank or fill hose but is limited to the engine fuel supply hose or carb issue.

[Huuligan]

Wondering why you don't run the blower all the time? I do.

[mmwjr]

Originally Posted by Huuligan

Wondering why you don't run the blower all the time? I do.

You shouldn’t need to. The blower is to evacuate and fumes prior to starting a gas engine. If fumes are accumulating while running you have an issue that needs to be resolved.

[Huuligan]

Originally Posted by mmwjr

You shouldn’t need to. The blower is to evacuate and fumes prior to starting a gas engine. If fumes are accumulating while running you have an issue that needs to be resolved.

All the more reason to run the blower while under way! Yes, the issue needs to be resolved but why wait till you have an explosion to do that? Just my common sense kicking in.

[mmwjr]

Originally Posted by Huuligan

All the more reason to run the blower while under way! Yes, the issue needs to be resolved but why wait till you have an explosion to do that? Just my common sense kicking in.

If there is a fuel leak running the blower will not prevent an explosion. Seen this happen more than once.

[Phillbo]

Fuel leak / smell = DO NOT START THIS BOAT UNTIL THE ISSUE IS FIXED.

[jparsons121]

Agreed!!!
If you smell fuel, shut down immediately. The vapors needed to ignite are already in the bilge and you can blow yourselves sky high. You will need to trace the fuel line and find the source before any further running. If they are carb’d engines it may be something as simple as a stuck float.

[speedcat]

Hi I have a different problem. I smell fuel after filling the tank. It goes away after a while. 1996 2400 SCR. I'm wondering if this is due to a bad fill hose, or bad gas tank vents? The survey said that one of the vents might be an issue. A pic shows that one (starboard I think) looks like it might be blocked. Could that cause a gas smell inside? Thanks all for your thoughts.

[mmwjr]

Originally Posted by speedcat

Hi I have a different problem. I smell fuel after filling the tank. It goes away after a while. 1996 2400 SCR. I'm wondering if this is due to a bad fill hose, or bad gas tank vents? The survey said that one of the vents might be an issue. A pic shows that one (starboard I think) looks like it might be blocked. Could that cause a gas smell inside? Thanks all for your thoughts.

Are you smelling gas in the cabin, engine compartment or on deck? Look for cranks in the fill hose. Starboard near mid-ship vent is the fuel tank. Don’t think it being clogged would cause fume smell but instead cause the fill neck to burp out gas when filling. A clogged vent can also cause fuel starvation of the engine resulting in it losing power after operating for ~30 minutes.

[speedcat]

Originally Posted by mmwjr

Are you smelling gas in the cabin, engine compartment or on deck? Look for cranks in the fill hose. Starboard near mid-ship vent is the fuel tank. Don’t think it being clogged would cause fume smell but instead cause the fill neck to burp out gas when filling. A clogged vent can also cause fuel starvation of the engine resulting in it losing power after operating for ~30 minutes.

Thanks Mike as always.

Pretty sure the smell was in all three places. If I leave the rear berth window closed, I think the smell is less in the cabin. Strangely it seemed more pronounced on deck (above ER / at helm) than it did in the ER. But I haven't really done a thorough check of this so that could be wrong. I don't see any gas in the bilge or ER so I assume this is just fumes. Again this goes away after a while and you never smell it again until the next fill up.

I checked and the gas tank vents are all new so checked with the prev owner and indeed he had replaced those after getting his survey. But I suppose the lines that feed those vents could be bad, or maybe blocked somehow.

I don't see any starvation issues. I do fill slowly to start because the first time I filled this boat, some gas came out onto the swim step.

I'll check for cracks in the fill hose. I'm worried that I won't be able to see the entire hose all the way to the tank... let me know if there are any tricks there or anything else I should know about the fill tube.

Thanks again.
-Speed
1996 2400 SCR

[jparsons121]

I’d verify the previous owners claim regarding the vents. On one of my previous boat the Perko vent fittings were replaced, but the vent hose wasn’t properly seated and was allowing vapors to escape. Didn’t smell anything at the time, until a mud wasp built a nest in the vent and the back pressure when I was filling up popped the hose right off the fitting. Then I smelled gas for sure.

[speedcat]

Originally Posted by jparsons121

I’d verify the previous owners claim regarding the vents. On one of my previous boat the Perko vent fittings were replaced, but the vent hose wasn’t properly seated and was allowing vapors to escape. Didn’t smell anything at the time, until a mud wasp built a nest in the vent and the back pressure when I was filling up popped the hose right off the fitting. Then I smelled gas for sure.

Thanks. Yes that's along the lines of what I was thinking too.