Help regarding steam or smoke coming from an exhaust component, time sensitive..

[chrisncate]

,uiio

[RichH]

Difficult to follow your 'explanation'.
But if the 'steam' is coming from the area of the 'threads' at the BASE of the U, then there are TWO possibilities:

1. The threads on the elbow have been 'hammered' due to engine vibration and the injection elbow is now loose from the exhaust manifold flange etc. .... if so reseat with automotive 'muffler cement' OR replace the elbow.

2. restriction in the exhaust system but downstream of the injection elbow.... ie.: coke or accumulated calcium carbonates immediately downstream of the water injection port PLUS loose threads on the injection elbow.

No. 1 has a higher probability especially if the injection elbow is a retrofit ALUMINUM casting. If the threads are 'relieved', You'll probably also see a 'soot' accumulation near the threads ... or 'all over the place' as a thin film - use your clean finger and wipe the adjacent surfaces. Most times to fix you can simply put a pipe wrench on the inj. elbow, or if the 'geometry' restrains the 'tightening' then apply 'muffler cement' and retighten .... but get a spare elbow as you will soon need it.

[scottyt]

i would check for a hole or crack in the pipe. that upside down u is the spot where cooling water get injected into the exhaust pipe. it is also the notorious spot for corrosion on yanmars. the reason for the water coming out being cold is simple, our water is so cold right now it does not take much to keep the engine cold, most of the water is bypassing the thermostat, thats a good sign.

on a raw water cooled engine its called the mixing elbow, it might be on the fresh water cooling too.

in all honesty run it as it is, but keep the cover off the motor to keep an eye on it, and stay out of the cabin. it might get worse real fast, or make it all the way. either way you are probably getting some carbon monoxide out of the elbow. but be prepared to pay for new parts either way.

[CalebD]

No takers?
I'll start with some questions and grand speculations since I'm no Yanny expert.
Q: Raw water or Fresh water cooled (anti-freeze) ? I'd guess FWC from the pic.
Q: How old or new is the engine? Original? What boat installed in?
Q: Does the white smoke dissipate pretty quickly or is it persistent?

Grand speculations:
- The silver upside down 'U' shaped thingy seems to be where your raw water enters your exhaust. Call it the exhaust mixing elbow or something like that. Clearly it should not be venting steam in your engine compartment so that is problem #1.
- How did problem #1 arise? It could be that water was left in that fitting and froze. We've had a few months of real winter in NY and probably the same where you are.
-- If it was cold enough to freeze then I'd question how well your engine was winterized in the first place. If the raw water pump was not drained or at least allowed to suck through a gallon or 2 of anti-freeze then your raw water pump impeller may also need looking at or replacing.
-- If it was cold enough to freeze then I'd also look into the thermostat which, if malfunctioning could cause cold(er) water to come out of the exhaust. There is a thing called a 'bypass loop' on some engines that is controlled by the thermostat which might keep cooling water from entering the engine block by sending it out the bypass loop.

Here is a temporary fix for the symptom, but maybe not the cause: JB Weld.
"It stays pliable for about 30 minutes after mixing, sets in 4-6 hours, and cures fully in 15-24 hours. It's water-proof; petroleum-, chemical-, and acid-resistent; resists shock, vibration, and extreme temperature fluctuations, and withstands temperatures up to 500° F. J-B WELD is super strong, non-toxic, and safe to use. Before it sets, you can clean up with soap and water."
J-B Weld Company - J-B WELD Product Information
I'm not sure you have the time to even try this as this high temp. epoxy cures in 15 - 24 hours or so.
Be glad you also have sails. Good luck.

[scottyt]

Originally Posted by chrisncate

I could not find any cracks, holes or compromises visually, or by feeling for one (good sign I guess?).

By getting bad real fast, do you mean overheating or just the possibility of carbon monoxide? As for death by carbon monoxide, no worries - we will both be in the cockpit the whole way.

it could be loose threads as was stated

as for getting bad real fast, that would be a big hole in the pipe allowing 95% of the exhaust to exit in the boat. but it should not do any other damage, except the mess of the water and exhaust getting everywhere. as long as water is coming out it should not do anymore damage to the elbow as it will be cooled by the water.

you could do the jb weld to close up the threads on the bottom for safety for the trip, if you put a heater on the joint and the jb weld it will cure in 2 or 3 hours.

[LakeSuperiorGeezer]

If you put diesel carbon monoxide in a search engine you will find that there is not enough carbon monoxide in diesel exhaust to harm a person.

About finding the exhaust leak, start the engine and move your hand around where you think the leak is coming from. Also check beyond the elbow since I do not see any exhaust residue at the elbow. Because the exhaust comes out of the cylinders in a burst when an exhaust valve opens, you can easily feel these pulses of gas when you put your hand near it. Do this after just staring the engine since you do not want to get burned from a warmed up engine. Also be aware of any belts and moving parts driven by belts. Turbo chargers even the pulses out so that makes it harder to detect. It could be an exhaust manifold gasket, but this gives a sharp popping noise. The ‘white smoke’ could be unburned diesel, which can happen on cold days first starting up, or because the diesel is not burning because of poor compression. There will be a strong odor of raw diesel with the ‘white smoke’ if you get down wind of it. If the engine has not had time to warm up, I doubt it is steam, but unburned diesel so not a worry. By the way, did you determine if there was any water in the diesel? Very important to know this as you do not want an engine quitting when you need it the most.

[jackdale]

Another - expensive possibility.

Blown head gasket and a leak near the elbow.

[scottyt]

jack i would agree but he should be able to hear a bad gasket.

[RichH]

Simple test for loose threads on the inverted U shaped injection elbow: when the engine is COLD grab hold of it and forcibly (use large pipe wrench if needed) try to 'wiggle' it, if anything 'moves' the threads are loose/hammered.

If you use JB Weld, epoxy, or anyother 'glue' but 'muffler cement' or other 'fine refactory cement' on a hot exhaust component ... youll just cause smoke and stink and will then immediately loosen when 'cooked off'.

[MacGyverRI]

are you sure the hose fittings are tight where they screw into the manifold? Use pink or green teflon tape (fyi, water keeps the elbows cool) or Plumbers putty on the pipe thread fittings.

p.s. remember to re-winterize it after you're back! the way you said that you did it is fine.