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Yanmar 3GM white smoke

May 16, 2021
6
Catalina Catalina 320 Newcastle
Has anyone experienced this on their engine? The engine is 18 years old and the meter shows 1100 hours. It starts first time, doesn't blow smoke when it's tied up to the marina and run at full power. I've only noticed it after motoring along at about 2000rpm for a while. I've only owned the boat a few months, so I don't really know how long it's been doing this.
 

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RitSim

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Jan 29, 2018
234
Beneteau 411 Branford
I would plan a compression check. Harbor Freight has a diesel compression test set. Be sure to research whether you need metal seals under the injectors so you can put the engine back together.
 
Feb 14, 2014
5,582
Hunter 430 Waveland, MS
Looks like steam vapor to me.

Check your water flow injection to the exhaust riser. A restriction in sea water flow can cause this.

Does the exhaust still "spit and surge" on exit of the boat?
Jim...
 
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Feb 21, 2013
3,462
Hunter 46 Point Richmond, CA
What happens when you operate at higher rpm? When was the mixing elbow last replaced? Are you getting sufficient water coming out of the exhaust, if not you may have a clogged mixing elbow? Have you checked coolant level? Lots of potential causes like a fouled mixing elbow indicating a need for replacement and others identified in this article: The 3 Causes of White Smoke From A Diesel And What To Do Next - Learn Diesels

Same question came up on this thread with lots of potential causes identified: White smoke in exhaust-Yanmar diesel | Sailboat Owners Forums
 
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May 16, 2021
6
Catalina Catalina 320 Newcastle
Thanks for the replies. I did wonder if it was steam. It dissipates very quickly behind the boat. The engine is also running at about 175-180 degrees, which seems hot, but I'm not sure what the normal range is. It is discharging water through the exhaust, but I'm not sure it's enough. The coolant level is fine and doesn't change.
 
Feb 21, 2013
3,462
Hunter 46 Point Richmond, CA
Brucegra..........thanks for the update. Unless you have records when the last engine service was performed suggest doing one.........particularily oil/fuel filters, engine oil and raw water impeller replacement and heat exchanger, drive train and exhaust elbow inspections. That is what I do on every boat I purchase. No service history on my Hunter 46 so has a complete engine service (500 hours). On the otherhand, a recent powerboat purchase I obtained the engine service records (2000 hours) from the diesel mechanic and they were last serviced 50 hours prior to purchase so good for 200 hours.
 
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Apr 22, 2011
718
Hunter 27 Pecan Grove, Oriental, NC
I also suspect the mixing elbow is causing the white smoke. Restricted flow of water into the exhaust elbow could raise the temperature of the elbow to the point that the water will be vaporized and exit the exhaust as steam. Also, the restriction will most likely cause the engine temperature to rise because of the reduced water flow through the heat exchanger.
Take the small hose off the top of the elbow and check for a restriction. If nothing is obvious there, you may need to remove the elbow for inspection.
 
Jul 5, 2011
584
Oday 28 Madison, CT
175-180 is typical for diesel inboards and is not, by itself, a steam generating temperature. Yes, a restriction seems probable. If you take a rag and carefully capture some water from the exhaust (to avoid getting a burn, not with bare hands) is that exhaust water really hot? What kind of water quantity coming out?
 
May 17, 2004
3,388
Beneteau Oceanis 37 LE Havre de Grace
Title says 3GM, not 3GM(F), so I presume it’s raw water cooled? Assuming that’s the case 175-180 does sound warmer than normal for raw water cooled engines. I agree with the others that it sounds like a cooling water restriction. In fact Nigel Calder’s book says “White smoke at high engine speeds and loads is almost certainly water vapor, most likely caused by reduced cooling water flows—check the raw-water system.” Also keep in mind that when looking at troubleshooting guides for land based engines they generally won’t consider any raw water cooling, so problems like that will be overlooked there.
 
Nov 22, 2011
957
Ericson 26-2 San Pedro, CA
Title says 3GM, not 3GM(F), so I presume it’s raw water cooled? Assuming that’s the case 175-180 does sound warmer than normal for raw water cooled engines. I agree with the others that it sounds like a cooling water restriction. In fact Nigel Calder’s book says “White smoke at high engine speeds and loads is almost certainly water vapor, most likely caused by reduced cooling water flows—check the raw-water system.” Also keep in mind that when looking at troubleshooting guides for land based engines they generally won’t consider any raw water cooling, so problems like that will be overlooked there.
He referred to the coolant level in post #6.
 
Jan 7, 2011
2,777
Oday 322 East Chicago, IN
Title says 3GM, not 3GM(F), so I presume it’s raw water cooled? Assuming that’s the case 175-180 does sound warmer than normal for raw water cooled engines. I agree with the others that it sounds like a cooling water restriction. In fact Nigel Calder’s book says “White smoke at high engine speeds and loads is almost certainly water vapor, most likely caused by reduced cooling water flows—check the raw-water system.” Also keep in mind that when looking at troubleshooting guides for land based engines they generally won’t consider any raw water cooling, so problems like that will be overlooked there.
I have a 2GM20F, and one day I checked the exhaust water temp…was surprised to find the water pretty tepid…lake water was probably in the 60’s, but really surprised the water was barely warm.

Greg
 
May 16, 2021
6
Catalina Catalina 320 Newcastle
It is a 3GMF. I contacted a Yanmar dealer and they told me that when the thermostat is fully open, the temp should be around 185, so it doesn’t seem too hot. Thanks for all the suggestions. I’ll test them out in the next week or two and post an update when I work something out.
 

Guan

.
Jul 18, 2011
138
Beneteau Oceanis 361 Vancouver
I had same be problems of white smoke with my Westerbeke B30 comes on after 20 mins. see feeds...Old Smoky...got v good dedicated advice in this blog.
changed all fuel filter etc and fuel. now only black smoke when do I'll throttle.
 
May 16, 2021
6
Catalina Catalina 320 Newcastle
I've checked out as much as I can and can't find anything mechanically wrong yet, but I've noticed that every time the steam has appeared, the humidity is around 90-100%. When it's around 30-40%, it all looks normal. The water temperature is about 50 degrees here right now, so does anyone know if it's possible this isn't really a problem after all, just hot exhaust being cooled by cold water on a humid day? Is this not even steam? This is a 3GM30F by the way. I didn't put the full details in the first post.
 
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