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Discussion Starter #1 (Edited)
Hi folks. I have a Yanmar 3hm35f engine Fresh water cooled with about 2500 hours. Engine generates some white smoke when running which appears to be water vapor. Does not smell like fuel, no sheen on water, much less visible on dry air days, dissipates quickly. Not dependent on engine temperature. Above water engine exhaust outlet. It has been like this ever since I bought the boat 1.5 years ago. Otherwise engine running fine, not taking oil, not loosing coolant. Any reason for concern?
 

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Discussion Starter #3
have you checked the exhaust elbow internal crack or leak can cause it to produce steam.
Thanks for the suggestion. And no, I haven’t checked that. Doesn’t look like a simple job. Would I be replacing that mixing elbow in that case? Meaning, having it on hand just in case? Any idea on the cost of this part? Preferred replacement source? My current elbow is not stainless steel.
 

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I have a Yanmar 3gm 30. Mine did the same thing but I have way fewer hours on mine. The first time it did that I concluded that it may be exhaust elbow or dirty injectors. I have owned my boat for close to 20 years and replaced the elbow about 10 years ago. It was actually a pretty easy job, 4 bolts and two hoses, 4 clamps/6 if you include the two that i removed on the waterlift muffler since I replaced the exhaust hose at the same time.

My recollection was that the parts were around $150 with the gasket. The job was not at all hard or time consuming but I have easy access to that side of the engine and the nuts were not frozen on the studs.

The one I had looked like this: https://www.ebay.com/i/353041487977?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=353041487977&targetid=883323210413&device=c&mktype=pla&googleloc=1018507&poi=&campaignid=9418889660&mkgroupid=92908014142&rlsatarget=pla-883323210413&abcId=1141016&merchantid=6296724&gclid=CjwKCAjw5cL2BRASEiwAENqAPvj5IAF9QQ3LiePMw5MBGgAYgBpTNQksqVmxuImerT3o6T-TGtWAtxoCDM8QAvD_BwE

I also ran injector cleaner through my fuel tan periodically and which also seems to help as well.

Jeff
 

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first is it a 3hm35f or a 3gm30f never heard of a 3gm35f doesn't really because the elbow would be the same. i should ask how much water do you have coming out of the exhaust when running. if the water is not flow enough the water will turn to steam. is this the one https://hdimarine.net/product/gm-stainless-steel-mixing-elbow/
 

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I have a Yanmar 3gm 30.
I also ran injector cleaner through my fuel tan periodically and which also seems to help as well.

Jeff
Jeff- Can I ask which injector cleaner you use? My impression has always been that most "engine cleaner/injector cleaner" products are snake oil (for all I know, snake oil might very well dissolve crap in injectors).

Thanks.
 

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Discussion Starter #7
Thanks guys. ❤ The access to the elbow is not too awful but the bolts look mighty rusty. I might tackle the elbow swap myself.
There is good water flow out of the exhaust and engine is not overheating when run at high rpms for an extended time.
 

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Jeff- Can I ask which injector cleaner you use? My impression has always been that most "engine cleaner/injector cleaner" products are snake oil (for all I know, snake oil might very well dissolve crap in injectors).

Thanks.
I had usually purchased one from the Yanmar dealer in town. I also used one of the big name brands that I picked up at West Marine since I work there part time and could use my employee discount. I don't recall which brand.

Jeff
 

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PB Blaster on the bolts for a few days before un doing them, replace with Stainless and high temp never seize
Never seize for sure. Don't know why they come from the manufacturer otherwise. I disagree about stainless. This is one place for regular steel.

Mark
 

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whats wrong with SS bolts in a cast iron engine block? the exhaust elbow is stainless steel. manufactures have been using SS bolts in cast iron keels ever since they discovered that the steel bolts are not a very good idea in cast iron.
 

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You might check the thermostat, although, I rarely find them defective. Still, they are a wear item and not terribly expensive. If was digging into it, I'd just replace it. Testing could only confirm your sanity, if it's not opening at the right temp.

I'd also consider descaling the raw water circuit. I prefer to circulate descaler through the whole circuit (I have an Hx, oil and tranny cooler and intercooler), but in many, simply removing the heat exhanger and descaling it is all there is to it. It's possible that cooling raw water is not circulating well enough.
 

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Is the white "smoke" not just steam? If it starts and runs OK and does not drink oil, then just leave it.
 

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Is the white "smoke" not just steam? If it starts and runs OK and does not drink oil, then just leave it.
Depending on how much, that may be reasonable short term advice. However, steam due to poor cooling circulation is not good. Heat wears engines. It's like smoking cigarettes, each individual occasion won't be deadly, but over the long term, it will be what kills you.
 
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