Diagnosis

K

kev88

New Member
Feb 17, 2007
43
Smith Lake, AL
I am a former SRO member and have a 2006 205 Sport with a 5.0 L carberated engine (50 hours). Upon cold starts I am seeing about 5 minutes of faint blue smoke and film on the water. I also get black "smudge" on my gel coat. This happened all last season and at the end of the season I took the boat in for warranty work and the mechanic adjusted the carb in case of a fuel/air mixture problem. He told me that the smudge was just exhaust and was normal, but I have been told by other boaters and dealers that I shouldn't see this and it should burn clean...I agree. The engine starts (cold) fine, idles fine and, operates fine at all RPM ranges. It's common for me to see steam from the exhaust in colder water temps and weather. Engine temp tops out at 160.

Also carb "breathes" loudly upon cold startup.

This would appear to be oil leaking somewhere and buring off, but strange for a new engine to do this. I have 6 months left on my engine warranty and feel like the dealer will tell me this is normal....I know it's not.

Any suggestions/advice would be appreciated...want to be "armed" when I take the boat in.

Thanks in advance!!

Kevin
 
Sounds like your engine may be running a little on the rich side. I would look at the choke. If you see black stuff floating on the water behind your exhaust, it is almost certain you are running rich.
 
Thanks goblue. The technician adjusted the carb last season...no change. Wouldn't a rich mixture produce black smoke? Also wouldn't the engine be hard to start and not run smoothly? I am seeing blueish smoke that goes away after about 5 minutes.

Thanks!
 
I agree, sounds like it's running rich.

Bought our boat used last year... Always started right up and ran good, however... it was running so rich it gave you a headache from the smell. Also, the back of the boat was black and rainbows in the water...

Took the carb off, rebuilt it. Checked adjustments, and timing and it runs MUCH better! Better GPH also.

Make sure the flame arrestor is clean also. Mine was all full of crud.
 
Thanks H20. I've got the smell too. Did the smell get better after the engine ran for awhile? I was noticing this weekend that my GPH did seem worse.

If the engine is running rich and the tech adjusted the carb last year, what could he have missed?

Thanks!
 
Yes, after running a bit the rich smell would get better, but I could still smell and see it it the water.

Hard to say what the tech missed... I do everything myself... I've too many bad experiences with auto and boat mechanics.
 
kev88 said:
If the engine is running rich and the tech adjusted the carb last year, what could he have missed?

Thanks!
Click to expand...
He could have adjusted it warm, probably did. Sounds like your problem is mainly when it is cold. Your choke might not be releasing fast enough. If it is still choking when it should not, you might hear that. It might be easy to get in there and look at what happens on a cold start. See what it does.

Also, if your flame arrestor is clogged, that will have the same effect as choking it.

I often think of oil leaking past the valve stems when an engine puts off smoke when first started. But that should not happen in an engine that is anywhere near new, and others here seem to recognize your symptoms more as carb related.
 
Thanks Dave

It sounds like I have a choke/carb issue that wasn't corrected properly last season. I did pull two plugs last week and they are fairly carbon coated.

Trying to rule out all possiblities here - I changed my oil the first time last season using 5 quarts (followed the techs recomendation). My oil pressure guage was "pegging out" at about 3500 rpm and the dipstick was showing a high level. I then drained off about a quart getting back in the normal range. Ran the boat a short time like this.

I don't think this would be the case, but could I have blown a seal somewhere with too much oil pressure?

Thanks again!
 
kev88 said:
I am a former SRO member and have a 2006 205 Sport with a 5.0 L carberated engine (50 hours). Upon cold starts I am seeing about 5 minutes of faint blue smoke and film on the water. I also get black "smudge" on my gel coat. This happened all last season and at the end of the season I took the boat in for warranty work and the mechanic adjusted the carb in case of a fuel/air mixture problem. He told me that the smudge was just exhaust and was normal, but I have been told by other boaters and dealers that I shouldn't see this and it should burn clean...I agree. The engine starts (cold) fine, idles fine and, operates fine at all RPM ranges. It's common for me to see steam from the exhaust in colder water temps and weather. Engine temp tops out at 160.

Also carb "breathes" loudly upon cold startup.

This would appear to be oil leaking somewhere and buring off, but strange for a new engine to do this. I have 6 months left on my engine warranty and feel like the dealer will tell me this is normal....I know it's not.

Any suggestions/advice would be appreciated...want to be "armed" when I take the boat in.

Thanks in advance!!

Kevin
Click to expand...



Kevin,

As mentioned by others, I would get the choke adjusted. The "breathing" loudly at startup is a result of the choke being partially closed and you are hearing the engine fighting for air. The reduced amount of air creates a rich mixture which washes the oil from the cylinder wall creating the blue haze you describe.

The fact that it goes away when the engine warms up is a very positive indicator that you did not harm the engine by overfilling it.

The only thing that is weird is the oil pressure gauge "pegging" which I'm going to basically ignore. Why? Because engine oil pumps are static devices meaning that they will remain constant. The oil pressure changes based on the rpms of the engine, the viscosity of the oil (which will change as it warms up) and what restricts it (oil filter/oil passages). They also have a pressure spring which will bleed off excessive oil pressure so that you won't blow the filter off the engine.

You would normally have to put in way more than one quart to cause a restriction that would drive oil pressure dramatically up.

That said, it's a five minute carb adjustment that needs to be done with the engine cold. I wish they were all this easy.....
 
Black Smoke is indicative of a Carb that's running too rich. Blue smoke is oil in the combustion chambers that's burning off.

If I were you I would try to get a technician out on the water with you at engine start up. He should be able to do a better diagnosis after seeing the smoke at start up and for the first few minutes you mention it lasts. The fact you see an oil film too leads me to believe you are getting oil in the combustion chambers possibly because of leaking valve stem seal(s) or bad guide(s). You could also pull the plugs and look at each one of them to see if one or more are blacker than the others or possibly oil covered too. That would pinpoint which cylinder(s) might be the culprit..
 
Dave S said:
Black Smoke is indicative of a Carb that's running too rich. Blue smoke is oil in the combustion chambers that's burning off.

If I were you I would try to get a technician out on the water with you at engine start up. He should be able to do a better diagnosis after seeing the smoke at start up and for the first few minutes you mention it lasts. The fact you see an oil film too leads me to believe you are getting oil in the combustion chambers possibly because of leaking valve stem seal(s) or bad guide(s). You could also pull the plugs and look at each one of them to see if one or more are blacker than the others or possibly oil covered too. That would pinpoint which cylinder(s) might be the culprit..
Click to expand...

Dave,

I would normally agree with you but the motor only has 50 hours on it and the problem goes away after it warms up. Valve seals, guides and rings usually keep smoking either respectively on acceleration (rings) and deceleration (valve seal and guides).

I have seen my share of those problems on rebuilt engines but rarely on an engine with 50 hours on it.

-John
 
kev88,

I really don't like all the symptoms you mention with a warranty about to expire. I agree that a choke sticking on is likely, but I am not convinced it is the only thing.

I don't like the steam you see, the carbon on the spark plug, and the maxed oil pressure gauge. I agree you should pull the plugs and look at them all. Keep track of which goes where. Use and empty egg carton or something. Then I suggest you do. or get done, a compression check. This should find leaking valve guides or a blown gasket. It would also give you a good snapshot of the engine condition for future reference.

I don't agree that valve guide problems continue after warmup. If you have oil coming down the valve stem from overhead, it usually is a small, slow process. It happens when the engine is sitting and not running. When you start the engine, then you burn out what leaked in while it was stopped. After that, for a smaller leak it won't be enough to see while running. That is my experience.
 
If your motor is still under warranty then I would have a qualified Mercury Technician take another look at it. We can all keep offering suggestions or opining about what we think the problem is but unless you are going to try and figure it all out yourself, you need that Merc Tech to give it another once over with you there and with the boat in the water. Then if you still don't like the explanations you are getting, call Mercury yourself armed with as much information as possible and explain what is happening.
 
Dave S. is right. Sorry for my last post, I sent it before I finished editing, I had too much help from my 2 year old grandson. I would not do a compression check until other items were checked and addressed, in the manner Dave S. recommends.
 
Wouldn't carbon on the plugs be a sign of a rich mixture?

I noticed the steam last season - tech said it was normal and as water and air temps rose it stopped. Risers and elbows are cool/warm to the touch at idle, however they are warm/hot after running at 3/4 throttle.....

Tech also told me the too much oil (1 quart) would not hurt anything....I drained it off anyway.

I think I am going to a different certified Merc service center for a diagnosis. I like my Sea Ray dealership, but based on past expereince I don't feel like they are going to take the time to diagnose this properly.

Thanks again for the input..it's tremendously helpful!
 
Kevin,

Find someone you are comfortable with that will honor the warranty. In regards to your question: Carbon buildup is a result of a rich condition. Given what you have described, the choke condition can create the carbon. It could also be a carb problem.

That's why you should talk to someone you trust to take a look at the issue.

-John
 
Thanks John....

I spoke with the tech yesterday afternoon. My engine has the turn key start system, which I think was introduced in 2006. He said with this system there is not a choke and the 6 minutes (to be exact) of "breathing" is normal. He was actually very techical in his explanation of how it works. Film on the water, also normal and one would see this with a car engine if the exhaust were submerged. Smudge on the gel coat...normal.

Great guy and he's always been a straight shooter. This is not the same tech that adjusted my carb last season.

Will prob. get a third opinion..... :smt101

Kevin
 
kev88 said:
Thanks John....

I spoke with the tech yesterday afternoon. My engine has the turn key start system, which I think was introduced in 2006. He said with this system there is not a choke and the 6 minutes (to be exact) of "breathing" is normal. He was actually very techical in his explanation of how it works. Film on the water, also normal and one would see this with a car engine if the exhaust were submerged. Smudge on the gel coat...normal.

Great guy and he's always been a straight shooter. This is not the same tech that adjusted my carb last season.

Will prob. get a third opinion..... :smt101

Kevin
Click to expand...


Kevin,

I haven't worked on a TKS carb yet. I know they use a fuel enrichment process instead of a choke. I'm starting to think your friend is right about his assessment. I'll see if I can get some technical data on the system and what adjustments can be made.

-John
 
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