5.0 fuel smell in exhaust and slightly hard to restart when warm.

94 5.0, carbed, SN OF157289
Starts pretty good cold, a couple pumps of the throttle and it usually fires right up.
Once warm the exhaust smells of gas and it takes several (3-4) seconds of cranking to fire up and, even then, I have to listen closely to hear it catch. If I give it some throttle it fires much more quickly and decisively.
Last tank full I ran some fuel system cleaner thru it and there MAY be some slight improvement in warm starting bu it may also be wishful thinking. Idle speed by the boat tach is 700-800rpm.

Engine runs great otherwise.

Been doibg some reading and the only adjustments I'm seeing are idle speed, idle mixture and choke. And float adjustment inside the carb but I don't appear to be experiencing flooding or starving issues.

So, any suggestions on where to start to get rid of the odor and improve warm start?

Take off your flame arrestor, and check to see if it needs a cleaning?

I have the same problem it starts great and runs like a champ but after awhile it will dye down and stall out I have run lots of fuel through this boat and plenty of cleaner but still is doing the same thing a boat mechanic told me to run plenty of fuel stayblizer

Thanks Mike, I will look. Right now I'm thinking the fuel smell is a mixture adjustment and the harder srarting may be a choke issue?

Turbo, thanks for the reply but that's not my issue. My boat runs great all day and never loses power nor does it ever stall. I just have the fuel smell at idle and slightly long cranking with warm start.

Anyone else have any thoughts?

This is a 94' with a carb? Not fuel injection? Okay, check the operation of your choke, it should be fully off at operating temp.

Yes, carbed, def not FI.
Will be launching in about 30 min. Will pull flame arrestor and check it out both cold and hot. Will also try to get more info on the carb.

Carb is a 2bbl. Not all that dirty but will do a spray down the throat and consider a clean and rebuild over the winter. Choke , when cold closes with about 1/8" gap left open and is opening fully when engine is at temp.

Again, engine runs great, just have fuel odor in exhaust and 2-4 seconds of cranking before it catches when at operating temp.

Once you get the engine running after a warm start, shut off the fuel valve. The engine will run for a min or so on the fuel in the carb bowl. If the fuel smell in the exhaust goes away in short order and the engine keeps running, you have a float level/valve issue in the carb.

Interesting test. I don't think I have a fuel shut off valve. I can improvise though. Thanks for the idea.

Fuel shut off valves are mandatory!

No,

fuel shut off valves are not manditory and rarely are installed in most pleasure boats.

They were common back in the days of hard fuel lines and steel tanks............
They may be used with duel tanks but NOT on typical pleasure baots..

Anti-syphon valves are manditory


First thing is how are you trying to start it when warm? Are you starting it the same way you do when first starting when cold?

Method could be the issue so lets get that understood first.

If all is very good, when warm the olny thing needed to do is turn the key. NO throttle needed to pump gas into motor.

Normally pumping is only needed when cold.

Try pushing in the neutral start button on shifter, Move throttle handle to about 10:00 (do not pump back and forth) and then try to start.

In the end, what you smell is no big deal.......stand behind a non efi (carbed) non catylitic converter auto........you will smell gas when first started warm or cold.

No, I'm 99% sure I don't have a cut off valve.
FWIW, the boat is a '94 Monterey 206SCR bowrider.

My start procedure is, for a cold start, I pump the throttle 2 or 3 times and leave the throttle at somewhere near 1/2 and crank it up. It normally fires right up and I quickly back the throttle off so the engine idles at about 1000 rpm. It stays there about 30 seconds then move to neutral and I'm good to go.
On warm starts I normally don't touch the throttle, just turn the key. It usually will fire up within 3 seconds. But when it fires it just kind of speeds up slightly, so slightly that it can be hard to tell that its running. If I advance the throttle, as you suggest, to 10 or 11 oclock it starts much more quickly and decisively. I don't pump it when warm.

Hi Dave, I just read your post from 2014 and curious if you ever discovered what the problem was? I have a 2003 Bayliner having the exact same issue. It starts just fine cold, and after running awhile it has a bad fuel smell at idle (and right after turning off). It also has a long delay on turning over once it has been running awhile. It's also a bit louder than usual. Can't figure it out so curious what you discovered?

DaveG55 said:

94 5.0, carbed, SN OF157289
Starts pretty good cold, a couple pumps of the throttle and it usually fires right up.
Once warm the exhaust smells of gas and it takes several (3-4) seconds of cranking to fire up and, even then, I have to listen closely to hear it catch. If I give it some throttle it fires much more quickly and decisively.
Last tank full I ran some fuel system cleaner thru it and there MAY be some slight improvement in warm starting bu it may also be wishful thinking. Idle speed by the boat tach is 700-800rpm.

Engine runs great otherwise.

Been doibg some reading and the only adjustments I'm seeing are idle speed, idle mixture and choke. And float adjustment inside the carb but I don't appear to be experiencing flooding or starving issues.

So, any suggestions on where to start to get rid of the odor and improve warm start?

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