Yanmar 3GM30 white smoke (help)

[ShelleySailor]

I got a 1997 Yanmar 3GM30F with about 1,400 hours in my Hunter 34. Lately the engine has been hard to start. When it starts it idles rough as if it is running on 2 cyclinders, the engine just shakes and vibrates a lot, if I push it to increase RPM after about 2-3 minutes it smooths out at same time when I crank it white smoke comes out of the exaust and it is smoke and not vapor. After it starts it has a lot of white smoke until I put it in gear and get going. Under load at 2300 RPMs it runs fine and the smoke goes away. I should add there is an oily sheen in the water when its blowing white smoke. If ran for 15-20 mins it will start right up and have no smoke and run fine for the rest of the day. Next morning it will do the same thing as before.
Any ideas?
Thanks in advance!

[gonesail]

not that it will fix your problems .. but have you checked or replaced the mixing elbow lately?

[Compass790]

Injectors is the next thing to check after mixing elbow. If you are mechanically inclined its easy, just follow instruction in service manual.

You can isolate the problem cylinders by loosening the injector line nuts one at a time whilst its idling after start.
The oily sheen in the water is unburnt diesel.
Check mixing elbow first though if you havent done it recently.

[ShelleySailor]

Thank you for the ideas, the boat is new to me according to the previous owner the mixing elbow was replaced in the last 2 years.

[jt11791]

It's the injectors.

[Wotname]

You can isolate the problem cylinders by operating the decompression levers one at a time whilst its idling after start.

[ShelleySailor]

Originally Posted by Wotname

You can isolate the problem cylinders by operating the decompression levers one at a time whilst its idling after start.

Is it ok to turn them while the engine is running? I will try that this weekend when next on the boat

[Compass790]

Originally Posted by ShelleySailor

Is it ok to turn them while the engine is running? I will try that this weekend when next on the boat

They say in the manual not to do it to stop the engine but I dont see a problem with it. I use the decompression lever all the time to spin the engine up ( single cylinder ) the valve hits the piston in our case but it just knocks the operating lever on my hand, it doesnt do any damage. I do it to get oil pressure up before ignition.

i didnt realise the levers worked individually on the 3gm30.
Wottie came up with easier way than cracking injector line nuts.


are you sure the P.O. told you the truth about elbow replacement?. If confident he is go straight to injectors.

[ShelleySailor]

well I think he told me the truth and it does look newer than the engine. One of the injectors (#1) is rusted the other 2 look in good shape I would suspect that one is the culprit. I guess if I lift that decompression lever and start the engine it would sound the same as it does now? I suppose that is the logic of this test.

[Compass790]

Yes, whilst it is missing there will be no change in engine note if you decompress faulty cylinder.
When you say the injector is rusty i assume you mean externally? If so that doesnt mean much, it's the internals that matter

[ShelleySailor]

Yes, I meant rusty looking externally.
Maybe some salt water or corrosive liquid dripped on it.

[Wotname]

Agree that external rust tells us nothing about the inside of the injector. It does tell us it may be more difficult to remove the rusty injector than the others - don't ask why I know this .

The manual tells us not to use the decompression levers to STOP the engine and tells us the reason is because it leaves unburnt fuel in the cylinder - which is not good in the long term. Using the STOP cable / lever does not leave fuel in the cylinder.

So yes, you can use the decompression levers for all sorts of things - diagnostics, bleeding, raising initial oil pressure after a filter change, starting with a weak battery and so on. Use them as intended and they become your best friend.

[PaulvR]

Have you checked the water trap in the raycor? Water causes white smoke.
Also the hard start might be an initial slug of water??
The sheen may be unburned diesel as the engine tries to burn the water/fuel mix?

[sinnerman]

Originally Posted by ShelleySailor

Is it ok to turn them while the engine is running? I will try that this weekend when next on the boat

NOT recommended. It can damage the decompression levers/valves.

Find an injector shop near your home. Pull the injectors and bring them in for service.

They will test them, [cracking pressure and if they leak (dribble fuel) after firing], clean them and retest then. They may replace the nozzles assy. Probably cost you $250 for all three.

You will need the crush washers that go under the injectors (remove the old ones when you pull the injectors). The injector shop should supply new washers with the repaired units...

cheers.

[RLaird]

Might want to check your oil
If overfilled May be faulty injector
Also might do an oil change and inspect for water in the oil by separation
Note that fuel will mix with and thin the oil while water will likely turn it grayish / milky