7.4L expelling fuel/oil out exhaust creates sheen on water

[Triniborn]

2001 Sea Ray Sundancer 340 w/ twin 7.4L MPI engines. 670 hrs.

Starboard engine is expelling fuel out the exhaust and putting a sheen on the water. Spark plugs indicate that the engine is running rich. Other than the fuel smell and the sheen the engine idles and runs fine.

I’ve tried bypassing the fuel cooler, had all the injectors tested, replaced MAP sensor while plenum was off, replaced spark plugs, confirm distributor contact points are free from corrosion. There are two fuel pressure regulators (FPR); one on the fuel rail, and one above the fuel cooler. I confirmed fuel pressure at 38psi, when vacuum line is removed from either FPR pressure increases to ~43psi, which tells me the FPRs are doing their job. Compression checked all cylinders as well.

Any other ideas that would produce fuel sheen on the water out of the exhaust?

Thanks!

FYI - All coolers were bypassed, except for the transmission cooler. The sheen is visible as soon as engine is started and doesn't change regardless of runtime/temperature.

UPDATE - Problem found. Bad oil cooler, read on for the details.

 

[Stee6043]

My 1999 340 did this the first two years I owned it. Marina found zero issues. In the third year I believe I found the issue - I was idling it too much

Once we started getting her out and stretching her legs more regularly the sheen no longer appeared. I convinced myself it was just loading up when idling for too many weekend in a row.

I may be 100% incorrect on this. Correlation is not causation...

 

[scoflaw]

What about your coolant temp sensor? Might be telling your ecm that the motor is cold and to add more fuel. MPI's shouldn't load up no matter how long you idle around.

 

[km1125]

What about your coolant temp sensor? Might be telling your ecm that the motor is cold and to add more fuel. MPI's shouldn't load up no matter how long you idle around.

^^^^THIS, and easy to check too.

 

[markrsimon]

Are you positive its fuel and not oil? Went through this last year thinking it was fuel till I placed a drop of each (fuel/oil) next to the slick and did a comparison. Pulled the water hose from the oil cooler and voila - replaced both oil coolers. Trans coolers are getting swapped this spring.

So - for kicks, pull the water hoses on your oil and trans coolers just to verify.

I will say though - I did like 5-6 oil changes on that port engine in the spring to get the light milkshake out. When I did the winterization oil change - I was amazed at how clean the oil still was, compared to the stbd side. Thinking I’ll repeat the multiple oil changes on the stbd engine this year to get it cleaned out as well.

 

[sbw1]

My 1993 370 Express put out a sheen and fuel smell from the day it was brand new, fresh out of the box. Did it for the 13 years I owned the boat. The 454s were very solid engines.

 

[Triniborn]

Are you positive its fuel and not oil? Went through this last year thinking it was fuel till I placed a drop of each (fuel/oil) next to the slick and did a comparison. Pulled the water hose from the oil cooler and voila - replaced both oil coolers. Trans coolers are getting swapped this spring.

So - for kicks, pull the water hoses on your oil and trans coolers just to verify.

I will say though - I did like 5-6 oil changes on that port engine in the spring to get the light milkshake out. When I did the winterization oil change - I was amazed at how clean the oil still was, compared to the stbd side. Thinking I’ll repeat the multiple oil changes on the stbd engine this year to get it cleaned out as well.

I bypassed all coolers except the transmission cooler. It smells like fuel and the plugs show signs of the engine running rich.

 

[Triniborn]

^^^^THIS, and easy to check too.

I will check this sensor according to the service manual.

 

[Triniborn]

What about your coolant temp sensor? Might be telling your ecm that the motor is cold and to add more fuel. MPI's shouldn't load up no matter how long you idle around.

I will test the ECT sensor. Thanks.

 

[Triniborn]

My 1999 340 did this the first two years I owned it. Marina found zero issues. In the third year I believe I found the issue - I was idling it too much

Once we started getting her out and stretching her legs more regularly the sheen no longer appeared. I convinced myself it was just loading up when idling for too many weekend in a row.

I may be 100% incorrect on this. Correlation is not causation...

 

[Korkie]

I had same problem middle of last season. Checked with my Merc guy and he advised at 1200 hours, most common cause is the oil cooler He was correct. Changed it out and done. You can take it off and test it off the boat. You Tube it. Quite easy.

 

[bahamabreisus]

Start simple, how old are the plugs and wires.

 

[Thornton69]

Both engines are coming up to the same temperature at the dock?

 

[Pirate Lady]

My 1993 370 Express put out a sheen and fuel smell from the day it was brand new, fresh out of the box. Did it for the 13 years I owned the boat. The 454s were very solid engines. View attachment 120097

Damn that is pretty! They don’t make them like that anymore, where have I seen that style?

 

[Triniborn]

Start simple, how old are the plugs and wires.

New plugs, not sure about the wires.

 

[Triniborn]

Both engines are coming up to the same temperature at the dock?

Both engines idle and perform well. No overheating, identical gauge readings. Starboard is showing slight less oil pressure.

 

[Triniborn]

2001 Sea Ray Sundancer 340 w/ twin 7.4L MPI engines. 670 hrs.

Starboard engine is expelling fuel out the exhaust and putting a sheen on the water. Spark plugs indicate that the engine is running rich. Other than the fuel smell and the sheen the engine idles and runs fine.

I’ve tried bypassing the fuel cooler, had all the injectors tested, replaced MAP sensor while plenum was off, replaced spark plugs, confirm distributor contact points are free from corrosion. There are two fuel pressure regulators (FPR); one on the fuel rail, and one above the fuel cooler. I confirmed fuel pressure at 38psi, when vacuum line is removed from either FPR pressure increases to ~43psi, which tells me the FPRs are doing their job. Compression checked all cylinders as well.

Any other ideas that would produce fuel sheen on the water out of the exhaust?

Thanks!

UPDATE: I swapped IAC and ECM from the port engine and problem remains.

 

[Triniborn]

Are you positive its fuel and not oil? Went through this last year thinking it was fuel till I placed a drop of each (fuel/oil) next to the slick and did a comparison. Pulled the water hose from the oil cooler and voila - replaced both oil coolers. Trans coolers are getting swapped this spring.

So - for kicks, pull the water hoses on your oil and trans coolers just to verify.

I will say though - I did like 5-6 oil changes on that port engine in the spring to get the light milkshake out. When I did the winterization oil change - I was amazed at how clean the oil still was, compared to the stbd side. Thinking I’ll repeat the multiple oil changes on the stbd engine this year to get it cleaned out as well.

I bypassed all coolers except for the transmission cooler.

 

[Triniborn]

Start simple, how old are the plugs and wires.

Both engines are coming up to the same temperature at the dock?

 

[Triniborn]

I had same problem middle of last season. Checked with my Merc guy and he advised at 1200 hours, most common cause is the oil cooler He was correct. Changed it out and done. You can take it off and test it off the boat. You Tube it. Quite easy.

Bypassed all coolers, except for transmission cooler