Yanmar 240 Rebuild still smoking?

[tisho]

Hello all,

I need some advice. I have a 34' Mainship Pilot with twin 240 Yanmar diesel engines. I had an oil line blow and thereby ruin the Strbd engine and had to be rebuilt. I rebuilt them both at the same time as the work involved made that seem logical. The problem.... after the rebuild, the SStrbd engine smokes at about 1200 to 1600 rpms, quite a bit. It doesn't do it at the dock, nor in the first hour of running. After I have been up to 17knts (2600 rpm's ) for about 40 minutes or so, then slow down to the lower Rpm's we get the smoke and it doesn't quit. Port side has no problems and is clean. I am told by the guys that rebuilt it that it is either not getting enough air or the fuel Injectors (I think) have to be redone again. They want me to run with the engine hatch open this weekend and see if it does it again. Personally, we have had a dozen problems since the rebuild with the Strbd engine, I don't think it is the air flow. Early on when when first put it into the water, the engine was idling very rough. Eventually, on a sea trial with the mechanics, they heard what I heard and adjusted it and not it idles smoothly. Possible they over adjusted it? Any advice appreciated.

Tish

 

[DavidM]

Running it with the hatch open is to eliminate an airflow restriction to the engine caused by insufficient vent area. But if the port engine runs clean, I doubt it as well as it shouldn't wait an hour to start smoking if an air restriction is the cause.

Sounds like a turbo or injector problem. In my mind it is more likely the turbo isn't operating correctly. Maybe when it warms up the turbo binds a bit causing low air flow.

Take the air filter off and spin the turbo blades by hand. Try it after the engine is good and warm and is smoking. Shut it down and quickly try to spin it. If it doesn't spin freely, it needs to be rebuilt.

David

 

[Ski in NC]

What color smoke at 1600? Whitish/blue/grey? Or black? Makes a difference in troubleshooting.

Did they remove the injector pump during rebuild? When reinstalled, timing can be off and that can make smoke.

What was done on the rebuild? Usually loss of oil pressure hits bearings and can scuff pistons. Maybe wipe turbo.

 

[tisho]

The smoke is Black.Everything was removed and broken down during rebuild. The injectors were removed and remachined (not sure if that is right terminology). Complete teardown and rebuild of engine.

 

[jleonard]

Sounds like it might be an injection pump adjustment.

 

[Comodave]

I agree that it probably isn’t an air flow issue, but open the hatch and run it just so they can’t say that is the problem. Simple thing to eliminate and get the shop to move on to the real problem.

 

[tisho]

Thanks a bunch, that's what they are saying, eliminate the air flow issue. Probably an injection pump issue

 

[Odysseyman]

Just out of curiosity. What does it cost to rebuild two yanmar 240’s? New cylinder sleeves? New pistons, rings?

 

[Arc]

1- too much fuel
2- not enough boost
3- loss of compression
4- tight valves

 

[Ski in NC]

Black smoke in this case is likely low charge air pressure (turbo boost). Measure that under load when smoke starts and compare to other (good) engine at same load/rpm.

Was turbo replaced or rebuilt? Could be an error in the rebuild or wrong new turbo installed.

Could be a problem with injectors or injector pump, but I would start with measuring boost first.

Could also be as simple as two compression washers under the injectors causing spray to hit bottom of head. Seen one of those and it threw us for a loop.

Edit: does engine still run rough at idle?