Yanmar 4J-TE smoke

[Takitimu]

I have an issue with exhaust smoke coming out inside my boat, but only when I'm 2200 RPM and above. I can't for the life of me find where the leak is coming from. I see no visible signs along the exhaust tube or on the engine. Any advice?

[neilpride]

White smoke or black smoke? Turbo and air filter ok?

[Takitimu]

It's black for sure. The soot was all over plastic things in the boat. We had the turbo replaced because we thought that was the issue because it was locked up. Wasn't the issue.

[CrispyCringle]

If you have carbon "all over" the boat, then it has to be leaving a black mark where it is leaking. Have a really good flashlight and a mirror on a stick and get intimate with your exhaust. You have to search around and behind every inch, not just the easy parts, starting from the head to the transom.

Keep following the exhaust until it exits the boat. With rubber exhaust hose, the leak can be anywhere along the length. Not just at the joints.

[jamhass]

I had a similar exhaust leak, not as bad as yours apparently. Hard to find, but it turned out to be a badly seated injector. Pulling, cleaning the seat and reinstalling fixed it.

[Oldwheels]

Probably need a good look at the exhaust elbow. I have the same engine. They corrode from the inside break thru. There is a aftermarket one that is cast and much better and less expensive.
Black is diesel fuel unburnt. Check exhaust system for obstruction.
New turbo??? ummm. Old one is still good? Possible inadequate air in. Check all flows. If possible check inlet manifold pressure.

[Takitimu]

Originally Posted by Oldwheels

Probably need a good look at the exhaust elbow. I have the same engine. They corrode from the inside break thru. There is a aftermarket one that is cast and much better and less expensive.
Black is diesel fuel unburnt. Check exhaust system for obstruction.
New turbo??? ummm. Old one is still good? Possible inadequate air in. Check all flows. If possible check inlet manifold pressure.

No, the old turbo was definitely locked up, the previous owner bought the spare turbo because the mechanic managed to unsense it lat time not so much when I got it so in went the spare. I'll check all the items people have suggested so far.

[skipperpete]

As Oldwheels suggested, the mixer elbow is a prime suspect but it should have been inspected while it was removed for the turbo swap. Other possibilities for the soot/smoke are excessive blow by or ( assuming localized black deposits) alternator belt dust. Does the engine run as it should? Any unusual noises or loss of power? There are several other places where exhaust gas can escape into the engine compartment but do the easy stuff first. Given that the turbo has seized twice, (probably due to turbine scroll corrosion from the wet exhaust) there’s a distinct possibility that the area inside the exhaust manifold where the turbo bolts on has also corroded through, it’s fairly common and quite difficult to see on the underside of the heat exchanger assembly but,again, should have been obvious with the turbo removed. Get a mirror and flashlight to view just directly under and in front of the turbo mounting face.

[Ericson38]

There is a specialized IHI Turbo steel shim type 3 hole triangular flange gasket between the turbo exhaust out and the Mixing Tee input. Make sure it is there and that the nuts are tight. Also there is a square 4 hole one between the exhaust manifold output and the turbo's turbine wheel input. Those nuts can be hard to get to, as well as the 3 on the turbo housing to mixing T ones.