Exhaust Temp

R

Ryan

New Member
Jun 27, 2007
299
Baltimore, MD
Boat Info
2006 52 Sedan Bridge
Engines
700 MAN's
I went our for a quick shake down ride today, everything seemed fine, but I noticed that my port exhaust temp was between 50 and 80 degrees higher (hotter) than the starboard side?

Does that mean anything? I have a call into the MAN tech, but I thought someone here may know..

All other numbers were almost identical between the engines.

Thanks in advance.
 
My first guess is would be reduced raw water flow... plugged strainer, plugged heat exchangers (from impeller pieces, scale, mud,etc), bad impeller, etc...

Didn't you run the boat aground in Rock Hall? Did you clean the raw water system after that? If not, I'll bet you have mud plugging up the circuit/heat exchangers.

When was the last time the impellers were inspected/changed?
 
Four Suns said:
My first guess is would be reduced raw water flow... plugged strainer, plugged heat exchangers (from impeller pieces, scale, mud,etc), bad impeller, etc...

Didn't you run the boat aground in Rock Hall? Did you clean the raw water system after that? If not, I'll bet you have mud plugging up the circuit/heat exchangers.

When was the last time the impellers were inspected/changed?
Click to expand...

Yes, I did clean the strainers, and had rid lyme run through the system. But I will check.

Impellers - Changed last year, probably only 60 hours max on them, but still the same ones from when I ran aground.

I will check both, but would you say the one clogged (or more clogged) is the one with the higher exhaust temp?

Sorry, I am the guy you described as "taking care of it with my checkbook", but I am really trying to learn and do more.

Why would the engine temps be the same, but the exhaust temps be different?

Thanks,
Ryan
 
This is why I'm installing a set of EGT guages on my mechanicals.....

I'll stab at this....You are getting Higher EGT and normal engine temps, because you don't have a catastrophic failure.....yet! You have enough raw water flow to cool the heat exchanger (and maintian normal engine temp), but less than normal raw water flow to maintain normal EGT.

The EGT guage is doing it's job and letting you know you need to do something 'before' something bad happens.
 
what you are seeing is "coolant temps"... (What Dom said)

An exhaust temp increase can be caused by an elevated temp in the air intake and so that means your aftercooler may be plugged or water is not flowing through it fast enough.

Rydlyme is not going to clean out heat exchangers filled with dirt. That requires some disassembly... (not that *I* would ever be stupid enough to run aground)

The other thing you can try is swap the sensors on your engines. I would do that first just to make sure you don't have a bad sensor.
 
Thanks Guys!

Gary - You mentioned air intake, do the K/N filters enter in to the equation anywhere? I have never cleaned them....

Do you think the sensors are in the metal elbow, that I see?
 
Ryan said:
Thanks Guys!

Gary - You mentioned air intake, do the K/N filters enter in to the equation anywhere? I have never cleaned them....

Do you think the sensors are in the metal elbow, that I see?
Click to expand...

I have no idea where the exhaust gas temp sensor is on your engines... you should find it though.. I doubt it's the one on your exhaust elbow as, if your boat is like mine, that is tied to your Sea Ray systems monitor and does not talk to the engine. It's just closes when the thing gets to a certain temp (like 250 ish) but does not broadcast actual temperatures.
 
OK, do the air filters have an impact on this problem? Would cleaning them help?
 
But it's still a good idea to clean them according to the manufacturer's schedule.
 
I'm a bit out of my knowledge comfort zone here (if there is such a thing), but elevated EGT can be attributed to engine overloading (fouled or dinged prop, maybe?), and clogged aftercoolers and air cleaners.

Do both engines achieve target rpm's at WOT?

Suggest you post on Boatdiesel, or you might PM Tony Athens...
 
Ryan,

As suggested one of the easiest things to do is switch sensors. All the electronics on boats these days love to mess with us...

Do you have a thermal gun meter? They are relatively inexpensive ($40-$80) and you could run one on each exhaust manifold to see if there is a temperature difference. Also good to have handy incase one of your other temperature gauges goes bad to confirm if there is a real problem or just the gauge. Either way my reasoning below may negate doing this anyway.

I do not have much experience with EGT's in boating applications but I am going to assume they are measuring the actual temperature of the exhuast gas and not the temperature of the manifold or exhaust housing (which is water cooled). Someone what actually knows correct me if I am wrong!

Because Exhaust Gas Temperature meters typically measure the temperature of the exhaust gases coming out of the engine they work most accurately when mounted between the cylinder head and the turbo (do you know where your sensor is mounted?).

If your impeller or heat exchanger was clogged I'd expect you to see an increase in your engine's water temperature or air inlet temperature.

More often elevated EGT's are result of more load applied to an engine, an engine pushed past its capacity, or result of an internal mechanical issue. These may include a bad injector (improper fueling), damaged prop (increased load), increase in boost pressure (increased fuel requirement), etc.

How many hours are on your boat? Have you changed the fuel filters recently?

Are they 50deg off at idle, or only at cruise or WOT?
 
If the temps are OK at idle but not at cruise, that also may be another item that points to the pump impellers. The vanes may have 'set' over the winter and aren't producing enough volume volume to provide optimal cooling flow.

Doug
 
douglee25 said:
If the temps are OK at idle but not at cruise, that also may be another item that points to the pump impellers. The vanes may have 'set' over the winter and aren't producing enough volume volume to provide optimal cooling flow.

Doug
Click to expand...

My thoughts as well. I do not know MAN diesels, but this smells like a water volume issue. Open the impeller covers and look for trouble. I'd replace the impellers if they are due as well.
 
Asureyez said:
My thoughts as well. I do not know MAN diesels, but this smells like a water volume issue. Open the impeller covers and look for trouble. I'd replace the impellers if they are due as well.
Click to expand...

I also think he has so much Chesapeake mud in the bottom of his aftercooler that he has oysters living in it.
 
Does anyone know how & where the EGT gauge is installed on the diesels?

Ryan - Did you notice more diesel smoke coming out of your exhaust on one side vs. the other? Where you able to hit rated RPM's on both engines?

I may be way off here but in my experience if an aftercooler is clogged you'd see more diesel smoke and when coming up on plane the engine with the clogged aftercooler would take longer to rev-up.
 
Thanks everyone - I don't know where the sensors are, but I am going to find out, the MAN man is going to meet me and show me, he says the same thing, he run across a lot of bad sensors.

I do not have a thermal gun, but will get one.

Props were reconditioned and tuned after I ran aground and fuel filters were changed last week (as well as all oil and oil filters)

I will check the impellers, how big of a job is checking the aftercoolers on the MAN's? Anyone know?

The variation was there at idle through WOT at all speeds, seemed like it was more at higher RPM's than at idle, it ranged at times from 50 - 80 degrees.

I did not notice much smoke, except at start up, but that was the first real start of the season and after a fresh oil change, so I did not think much of it, it went away after running a little while.

I was able to hit rated RPM on both engines no problem.
 
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