Mercruiser 1.7 dti - water inside engine

HB22 · 31 March 2023, 19:53

Good morning,

I have this problem with a Mercruiser 1.7 DTI engine.

A few months ago I noticed that an engine was not running well and we noticed that there was sea water in the intake. The first thing I did was disassemble the intercooler to check it, and apparently everything was fine. I disassembled it and I've made a hot test to see if there are any leaks but it was Perfect. I reassembled it on the engine only to realize that it still had the same problem. But I am afraid the problem is not the intercooler. I disassembled the exhaust riser and it is clean, no leaks. So I really have no idea where this seawater coming into the engine is coming from. Has this happened to anyone? How did you solve it? The seawater and coolant exchanger is clean and with new gaskets, but in any case seawater passing through there cannot enter the intake (I think). There is some rust on the turbine. When I accelerate in neutral, it revs up but when I cruise, the engine does not rev up and releases black soot from the exhaust into the water.

Any advice? Thanks

beamishken · 31 March 2023, 21:08

Quote:

Originally Posted by HB22

Good morning,

I have this problem with a Mercruiser 1.7 DTI engine.

A few months ago I noticed that an engine was not running well and we noticed that there was sea water in the intake. The first thing I did was disassemble the intercooler to check it, and apparently everything was fine. I disassembled it and I've made a hot test to see if there are any leaks but it was Perfect. I reassembled it on the engine only to realize that it still had the same problem. But I am afraid the problem is not the intercooler. I disassembled the exhaust riser and it is clean, no leaks. So I really have no idea where this seawater coming into the engine is coming from. Has this happened to anyone? How did you solve it? The seawater and coolant exchanger is clean and with new gaskets, but in any case seawater passing through there cannot enter the intake (I think). There is some rust on the turbine. When I accelerate in neutral, it revs up but when I cruise, the engine does not rev up and releases black soot from the exhaust into the water.

Any advice? Thanks

These engines are very troublesome & it seems you have more than one fault first off the black smoke and lack of power suggests a turbo or boost problem have you checked the compressor wheel for lift? When you reach into the turbo after removing the air intake you should be able to spin the turbine shaft easily with thumb & finger & there should only be a small amount of lift. It is very common for the wastegate to stick & either overboost causing damage or no boost. If you remove the two bolts securing the boost controler at the top of the turbo you should be able to open & close the wastegate easily by pushing & pulling the rod.
The water in the intake can only get in via the intercooler or air intake. It is very common for the intercooler to corrode through on the end plates, did you strip it fully to check it & ensure the webs in the end caps of the cooler are fully intact?

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HB22 · 31 March 2023, 21:26

The main problem is that I find water in the intake, so it passes into the cylinders and then gets into the turbine. In my opinion, the turbine is inefficient because it gets air mixed with water. When I sailed to do a test, it did not produce black gaseous smoke, but it sootily deposits in the sea, as if it peels off areas where generally only exhaust gases pass through. Tomorrow I will check the wastegate, but if it was blocked, no water should enter the engine anyway. The air/seawater intercooler was completely opened, including the plates, and then resealed and tested with a high temperature hydraulic test and has no leaks.
I saw that the exhaust gas passes through the seawater/coolant exchanger before entering the turbine. Should I disassemble the exchanger and check? Could that be where the problem is?

Thanks for Your reply

HB22 · 31 March 2023, 21:37

I think that the inefficiency of the turbine is a consequence to the water in the exhaust, however I also find water in the intake before entering inside the cylinders, so I wonder if it is possible that from the turbine it goes inside the compressor and later end up in the air/water InterCooler and start the round again

beamishken · 31 March 2023, 22:15

Quote:

Originally Posted by HB22

The main problem is that I find water in the intake, so it passes into the cylinders and then gets into the turbine. In my opinion, the turbine is inefficient because it gets air mixed with water. When I sailed to do a test, it did not produce black gaseous smoke, but it sootily deposits in the sea, as if it peels off areas where generally only exhaust gases pass through. Tomorrow I will check the wastegate, but if it was blocked, no water should enter the engine anyway. The air/seawater intercooler was completely opened, including the plates, and then resealed and tested with a high temperature hydraulic test and has no leaks.

I saw that the exhaust gas passes through the seawater/coolant exchanger before entering the turbine. Should I disassemble the exchanger and check? Could that be where the problem is?

Thanks for Your reply

If there was enough water getting into the air intake to cause turbo problems on the exhaust side there would be other issues, the engine would probably hydraulic & not turn over. The engine would also knock badly if it was injesting water. How are you determining you have water in the intake and where is it collecting? The combined exhaust manifold/ heat exchanger is freshwater cooled the raw water runs inside the cooler core. For raw water to get to the exhaust via the manifold the freshwater system would also be contaminated with seawater

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HB22 · 31 March 2023, 22:32

After reassembling the air/water intercooler, seeing that the problem remained, I disassembled it again and there was water inside. Then I also disassembled the pipe that brings air to the cylinders and it was wet inside. I removed the injectors and there was water in the cylinders, which I removed by running the engine by hand and sending the water down the drain. The boat has two engines and I could swap the intercoolers, but I'm pretty sure the problem is not coming from there because I had it reassembled by a specialist company that also did a hydraulic test. After seeing that the problem was still there, I had another company do another hydraulic test and they confirmed that it has no leaks.

beamishken · 01 April 2023, 07:02

Is there water in the pipes feeding the intercooler? Have you checked the turbo for lift & confirmed its boosting? Easy to do with the pipes removed. You can run the engine with the boost pipes removed to determine whereabouts you are getting the water ingress into the system

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HB22 · 02 April 2023, 11:23

Yesterday I tried reassembling the water/air exchanger and leaving the intake disconnected, and it seems that the problem is not coming from that. However, I noticed that where the riser connects to the turbine, where the copper gasket is, a few drops of water come out and it is fresh water. The turbine is still not revving up, the wastegate is unlocked seems to be working properly. Probably when I tasted the water in the water/air exchanger it had salted somewhere else, I don't know, however the one I tasted yesterday at the turbine outlet was sweet. The only thing I am missing to check is the coolant/seawater exchanger and see if it is broken and at some point it is letting water pass into the exhaust. If the problem was the turbine, it shouldn't have water circulating anyway right?

beamishken · 02 April 2023, 11:51

Quote:

Originally Posted by HB22

Yesterday I tried reassembling the water/air exchanger and leaving the intake disconnected, and it seems that the problem is not coming from that. However, I noticed that where the riser connects to the turbine, where the copper gasket is, a few drops of water come out and it is fresh water. The turbine is still not revving up, the wastegate is unlocked seems to be working properly. Probably when I tasted the water in the water/air exchanger it had salted somewhere else, I don't know, however the one I tasted yesterday at the turbine outlet was sweet. The only thing I am missing to check is the coolant/seawater exchanger and see if it is broken and at some point it is letting water pass into the exhaust. If the problem was the turbine, it shouldn't have water circulating anyway right?

Okay you probably need to remove & service the heat exchanger/manifold to be sure that isnt leaking, it is a service item to periodically strip& acid clean & reseal the cooler core. Hopefully that will cure your water issue but its unlikely to cure your lack of power which is more likely a lack of boost. Your first picture of the turbine housing looks like expensive clearance to the turbine wheel but it may be the camera angle. Once the cooler is sorted I'd probably check the boost pressure under load

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