Smoking problems with an aging Yanmar 3GMD

[Docfmiles]

I need some advice because I've got some problems with my Yanmar. I purchased the vessel recently & hadn't had an opportunity to sail or fire the engine up because of health problems.

When I finally had a chance to use the engine, it fired right up. I had checked the oil, fuel & cooling systems and all seemed well.

The first thing I noted after starting it was a white colored exhaust at virtually every RPM coming from the exhaust. There seemed to be some water being spit out through the exhaust but in spurts and it looked like it was sufficient to cool it. The water gauge read 150 or so, and it seemed alright. The oil pressure stayed between 20 & 50 psi depending on RPM.

Since the previous owner advised me to keep it under 2200RPM, that's what I did.

The first day, all it did was smoke out the exhaust But with less power than I expected. Ran for about 6 hrs.

The second day, however was a different story. Besides the exhaust smoke, and after running for about 4 hrs, the engine started smoking from the cabin, no particular smell could be identified, so I suspected it was water.

I shut the engine down for about an hour while we were under sail and then restarted the engine. It still smoked from the exhaust, but after only ten minutes of running it once again started to smoke from inside the cabin and a few minutes later simply stopped. No annunciator was set off, but it stopped operating.

Approx thirty minutes later, I had to start the engine again. It still smoked from the exhaust, but the cabin quickly filled with smoke, too and after only a couple of minutes it stopped again. No awful sounds were made by the engine, but it didn't want to run.

I'd like to repair the problem. Any ideas where I should start?

[Neo]

What model number of the engine? Sea water cooled or fresh water cooled?

How much water would you estimate was coming out the exhaust per minute?

Is the smoke in the cabin the same as the smoke coming out the back, in terms of color, consistency, density, what not?

I PO told you to keep it under 2200 rpm. Yikes. Red flag. Sorry.

Depending on the model number, that sounds like it is too low. May indicate he was having the same problem to a lesser extent.

[Neo]

Oh. 3GMD. Missed that in the title. I assume that is not fresh water cooled.

[DeepFrz]

I think the best advice I could give you is to find a good diesel mechanic to help you.

[sailorchic34]

For a salt/ raw water cooled engine 150 degrees would be too hot. Should be running 135-140 max for raw water cooled. Though the guage could be off. Might need to delime the block/head with an acid solution. Some smoking with a rawv water cooled engine might be normal too.

Also check the discharge elbow for blockage. The 3gmd has a larger raw water pump and will lime up the discharge elbow.

Also there is a zinc attached to the inside plate attached to the rear of the head that needs to be changed out now and then. Fresh water engines don't have the zinc, BTW.

[Docfmiles]

Originally Posted by sailorchic34

For a salt/ raw water cooled engine 150 degrees would be too hot. Should be running 135-140 max for raw water cooled. Though the guage could be off. Might need to delime the block/head with an acid solution. Some smoking with a rawv water cooled engine might be normal too.

Also check the discharge elbow for blockage. The 3gmd has a larger raw water pump and will lime up the discharge elbow.

Also there is a zinc attached to the inside plate attached to the rear of the head that needs to be changed out now and then. Fresh water engines don't have the zinc, BTW.

Thanks for all the wisdom. I think the impeller and a strange setup before the water pump may be at fault. It required a "siphon" effect to allow water to get to the impeller. I'm trying to sort this out and will dismantle the water pump & check the impeller, too. If its gone, I now know to track down the pieces. A real learning experience! Oh, and I'll look into the sacrificial Zinc, too.

[Docfmiles]

Originally Posted by Neo

What model number of the engine? Sea water cooled or fresh water cooled?

How much water would you estimate was coming out the exhaust per minute?

Is the smoke in the cabin the same as the smoke coming out the back, in terms of color, consistency, density, what not?

I PO told you to keep it under 2200 rpm. Yikes. Red flag. Sorry.

Depending on the model number, that sounds like it is too low. May indicate he was having the same problem to a lesser extent.

Thanks for the advice, Neo.