C32 with two brown/dark turbochargers

Dirty aftercoolers or intercoolers. Is the engine room sooty? As those exhaust compensators are known to fail about every 2 years, and then soot up the entire engine room and well the soot gets through the air filters and clogs up the intercoolers and aftercoolers. Or it could be they had to shutdown the other engine and ran the boat on that engine at a higher rpm with a high load factor. Or they ran the boat with a crab trap line wrapped around the shaft and a much higher load factor. Are the hours even on both motors? It looks like an Azimut you're looking at, judging by the exhaust compensators? It might just be a few thousand to have the aftercooler and intercooler cleaned, tooooo ???.

How many hours on each motor? Post a picture of the other engine and any engine room pictures you may have.

I'd burnt paint. There are many reasons why this happens.

Offer enough that makes you comfortable to repair anything.

Can you turn the turbos by hand?

Being that "no tests can be performed", I highly doubt he can remove the air cleaner or exhaust to see if the turbo's turn by hand.

Hi,

I was assuming none that required running as its out of the water, let's see what the OP says.

One of which is loss of coolant circulation in that unit. Who knows why ... air lock maybe, the vent line has been very hot as well but the coolant line has not.

Elbow is an interesting CAT engine color.

That's another thought. Perhaps it ate a raw water impellor at cruise RPM and the exhaust got very hot and baked the paint off before they slowed the engine down. It's possible the engine didn't overheat due to the circulating coolant. Whatever happened, judging by the extent of surface rust, I'd tend to think it happened at least a year prior if not two years prior.

Hmmmm.

Have to wonder if daylight were trying to make its way through the elbow that was replaced by the CAT special paint, replacement - about where one sees rust on the replacement elbow?

Does not look as though the turbo was replaced at the same time.


Big red flag, maintenance wise.

Hi,

There is an exhaust blanket missing from the Turbo outlet to the stainless part above the bellows. The colour if the elbow is normal for the hot section.

There is no cooling water in that system between the Turbo turbine outlet and another position out of these photos.

If the raw water pump failed and the engine got hot enough to burn paint the black would be everywhere as these turbos are jacket water not raw water cooled.

Actually I think I've figured it out, now thinking about it. The exhaust compensators went bad and were replaced, and that is why they look fairly new in the photos and not as discolored with light surface rust and heat as I usually have seen them even after as short as 6 months old. Those look to have less than 20 hours on them. There used to be exhaust blankets that went from the turbo to the riser. When the compensators went bad, the exhaust leaking through them and associated soot were contained in the blanket and exited the blanket where it butts up to the turbo. The black you see on the turbo's are actually exhaust soot. When they removed the blankets to replace the compensators, they pretty much disintigrated and judging by the OP's story the boat is a repo and they didn't want to spend money on new blankets, or even so much as cleaning the soot off of the turbo's and touch up painting them.

I'm almost willing to bet money and had this same scenario occur on a similar boat (Azimut) that was only a few years old. When the compensators leaked exhaust gas, they pretty much cooked and destroyed the blankets and nobody replaced them. Given that scenario I wouldn't be worried about the motors. Azimut's are the only yachts I've seen use those compensators that look like that, and the longest I've ever gotten out of them before they crack and start throwing soot is about 2 1/2 years.

Like everyone said, if the motor overheated the coolant line would be discolored. The black is not from heat on the turbo paint but soot. If it was heat, the CAT paint would generally turn brown/dark brown, not black.

It's kind of hard to "overheat" the turbo on a diesel. To get enough heat to do that you would melt a few pistons and valves along the way and stop the engine long before the turbo is damaged. The coolant surrounding the turbo is to reduce heat radiated to the engine room, not to cool the turbine.

It doesn't take much heat to discolor paint. The turbo exhaust elbows look pretty normal as do the flex couplings. I don't see anything to indicate the sky has fallen but it does appear that there may have been an air lock preventing adequate coolant flow through the housing.

Take the air filter off and see if it spins freely.

Which really means nothing for troubleshooting or diagnostic purposes.

A lot of that discoloring looks exhaust leak related to me.