Gas smell at WOT

[MikeBravo]

I have had an issue with my port engine. My wot is only 4000 rpm, should be 4500-4600. And at this rpm I am getting a distinct raw gas smell. If I lower the rpm the smell goes away. I get no warnings or faults on my sc1000 gauges or VV Mobile. Any ideas?

 

[PlayDate]

When was the last time you changed the spark plugs? A misfire usually causes what you are experiencing. Replacing the plugs will give you a visual of which plug/wire may be the problem.

 

[MikeBravo]

When was the last time you changed the spark plugs? A misfire usually causes what you are experiencing. Replacing the plugs will give you a visual of which plug/wire may be the problem.

About 20 hrs ago. All has been fine until just recently.

 

[CliffA]

check your plug wires to be sure they are all seated well on the plugs and in the distributor cap.....

cliff

 

[MikeBravo]

I have done so and they are tight.

 

[techmitch]

My bet is on the wires.

 

[CliffA]

could be a dead spark plug....like John (aka PlayDate) suggested pull the plugs and see which one is wet with gas....then it is likely either that spark plug or that plug wire that is bad....

good luck...
cliff

 

[MikeBravo]

My bet is on the wires.

Could be. I have read on CSR that you can check the wires by firing up your engine in the dark and looking at the wires. I guess the wire or wires that don't glow would be the culprits. Sounds too easy to me.

 

[CliffA]

Could be. I have read on CSR that you can check the wires by firing up your engine in the dark and looking at the wires. I guess the wire or wires that don't glow would be the culprits. Sounds too easy to me.

sorry but its not really that easy...this test will show you if a plug wire is arching from a defect in the wire to a ground source when the engine is running and causing a mis-fire...you can have a bad plug wire with internal damage that will not show any signs of arching in the dark....the wires do not 'glow' in the dark...if a plug wire is arching it will look like sparks coming out of a specific spot on the wire....

cliff

 

[MikeBravo]

sorry but its not really that easy...this test will show you if a plug wire is arching from a defect in the wire to a ground source when the engine is running and causing a mis-fire...you can have a bad plug wire with internal damage that will not show any signs of arching in the dark....the wires do not 'glow' in the dark...if a plug wire is arching it will look like sparks coming out of a specific spot on the wire....

cliff

Yeah thought that sounded to easy. Well back into the engine room, I'll have my bandaids ready.

 

[techmitch]

Ignition/spark plug wires will sometimes only cause a misfire under load. High voltage (40 KV) will take the path of least resistance to ground. How old are your wires?

 

[MikeBravo]

Ignition/spark plug wires will sometimes only cause a misfire under load. High voltage (40 KV) will take the path of least resistance to ground. How old are your wires?

About 2 1/2 yeras old.

 

[scoflaw]

CF3 paint chip issue, clogs the FPR and creates sky high fuel pressure.

 

[Espos4]

A spray bottle to mist the wires could help pinpoint the issue.

I’d recommend following up with WD-40 to disperse the water droplets when you’re done.

 

[techmitch]

CF3 paint chip issue, clogs the FPR and creates sky high fuel pressure.

Thought of that initially but also thought I read that the issue was rectified by 06?

 

[Espos4]

Thought of that initially but also thought I read that the issue was rectified by 06?

Nope. Happened to my 2007.
It was replaced in 2016.

 

[techmitch]

Nope. Happened to my 2007.
It was replaced in 2016.

Wow, thanks for the correction. Does anybody know when the problem stopped?

 

[PlayDate]

sorry but its not really that easy...this test will show you if a plug wire is arching from a defect in the wire to a ground source when the engine is running and causing a mis-fire...you can have a bad plug wire with internal damage that will not show any signs of arching in the dark....the wires do not 'glow' in the dark...if a plug wire is arching it will look like sparks coming out of a specific spot on the wire....

cliff

Short of having an 8 lead oscilloscope wired to the engine with someone watching it as you run the boat.....looking at the spark plugs is your best path to find a bad plug or wire.

Depending on the effort you want to put in and what your time is worth to you.....sometimes it is far easier to replace the plugs and wires and just eliminate the problem or the possibility of a problem.

One of your current wires could have been compromised and it really isn't practical to run the boat at WOT and watch the plug wires. Oftentimes plug wires get cooked from a minor exhaust leak and then short out at high rpms. The miss is happening under load at high rpms which makes replacing the plugs and wires as the most sensible approach. You can always hang on to the old plugs and wires if they aren't the source of the problem.

Make sure the plugs are gapped correctly and the new boots are seated.

 

[PlayDate]

Wow, thanks for the correction. Does anybody know when the problem stopped?

Mitch,

The "new" Gen III version was released 2/1/2009 by Mercruiser. Owners have reported problems with some 2010 models which probably used leftover stock. I haven't heard of a problem on a 2011 boat which means their subcontractor finally understood the words: "stop painting the inside of the pump module".

 

[techmitch]

Thanks John, good info. Yea, that "sell till stock is depleted" thing really pisses me off!