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Old 11-30-2015, 03:48 PM   #1
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Steam in the exhaust

Is it ever normal to have stream coming from the exhaust? I have a 1978 Mainship with a Perkins T6.354. At WOT I see lots of stream coming from the exhaust. The cooling system is clear and clean, the engine temps are normal using an IR sensor at several locations. The EGT is 900 degrees f at 2400 RPMs, and 450 at 1800 RPMs. I replaced the wet elbow and installed a muffler and the stream persists. This is on San Francisco bay where the water temps are between 55 and 60 degrees. I have felt all around the wet elbow and there are no hot spots after the water injection port. Blow by seems nominal.

The only two pieces that are suspect are the water pump cam and the raw water intake grate on the underside of the hull. Is there a process for testing the raw water output? I've contemplated disconnecting the raw water injection hose at the elbow and seeing how much is getting put through by measuring the time to fill a five gallon bucket.

Also the last impellor came from West Marine. The sales guy just looked at a catalog of templates and sold me the one with the same diameter and number of vanes. I could imagine the stiffness of the vanes could make a difference.

I've heard of hotspots forming in the exhaust manifold than cause pockets on boiling water. I'm about to flush the manifold with Evapo-Rust since it appears to have scaling on the inside. There's a bolt on plate on the side of the manifold. I'm contemplating removing it but I'm concerned the bolts will shear off.

There is also blue smoke continuously but I think my turbo was leaking oil. I've rebuilt it and have not yet reinstalled it.

Thanks for the advice,
Robert
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Old 11-30-2015, 04:50 PM   #2
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Ninety percent of the time, steam in the exhaust is entirely normal and is the result of raw water and exhaust exit temperatures, ambient humidity, etc. My 370 hp Yanmar makes steam almost all of the time while underway.


But sometimes it is due to reduced raw water flow which can be caused by a number of issues. Your idea of removing the raw water hose and putting it in a bucket and timing the fill is good, as long as you do it right after starting so it doesn't overheat the exhaust system with no flow.


But you do need a spec to compare against. Some manufacturer's (Yanmar for example) give a spec, some don't. And the spec will usually be at wot which is hard to do. I would do it at half of wot rpm, not in gear- it won't matter that it isn't loaded, and double it for comparison. You will be close.


I think that flexibility of impeller blades is in the eye of the beholder and isn't relevant in any case to pump performance.


I doubt if cleaning your coolant side will affect exhaust steaming, but it can't hurt.




David
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Old 11-30-2015, 05:15 PM   #3
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Steam? Blue smoke too? In 1978, engine technology wasn't what it is today. EPA rules now mandate that diesel exhaust be virtually free of anything that would be visible, so no more blue exhaust, no more NOx, etc. In fact the clean exhaust is now often referred to as "just steam".
Even 1990s technology didn't eliminate blue, so as you look around your marina at others starting their engines, after letting them get cold, you will see both blue and steam.
Unless this is a new phenomenon, I wouldn't worry. If it is new, what has changed? Other than doing a fairly extensive bit of PM, you have not reported anything changing.
I wouldn't disconnect cooling water at the injection point. I would push an empty bucket down under the exhaust outlet and time it to fill. Usually just a visual on the stream is enough to confirm that you are getting good flow.
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Old 11-30-2015, 08:29 PM   #4
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I have twin Perkins 4.236 so I have the advantage of watching two engines simultaneously and comparing the two. My port side was showing a creeping temp and steam. The steam appeared months before any temp creep. I did a 4 hr flush of the HX, oil/tranny coolers and exhaust manifold with Barnacle Buster. All components remained as installed for the test with the upstream and downstream hoses disconnected to allow the flush hoses to be hooked up. A cheap $20 bilge pump from Walmart provided the flow.

The result was a 30 degree drop in my engine temp, no more steam and one happy customer. Kudos to dswizzler here on TF for the great advice!
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Old 11-30-2015, 09:45 PM   #5
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In the region we boat in humidity and ambient temperatures combine to make steam from a wet exhaust system a common occurrance. In the winter we have seen boats cruising in the islands with the entire transom and cockpit enveloped in steam.

We get steam from our two exhausts during the winter. One exhaust emits more steam then the other. When we first noticed this some 17 years ago we asked our diesel shop about it. Their reply was that the presence and amount of steam is dependent not only on temperature and humidity but also on the configuration of the exhaust system. Something as simple as a difference in the hose length between the exhaust elbow and the lift mufflers on a pair of engines can affect the presence and amount of steam emitted with the exhaust.

This is the situation in our boat with the port engine having a shorter connecting hose than the starboard engine. So this alone could be responsible for the differing amounts of steam we experience between port and starboard.

In the spring, summer, and fall we get no steam out of the exhausts. But we've observed some boats that do.
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Old 11-30-2015, 10:10 PM   #6
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Same as contrails with aircraft. Sometimes they form, sometimes not. Both contrails and steam from boat exhaust are saturated water vapor. Highly dependent on atmospheric conditions and wet exhaust temp.
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Old 11-30-2015, 10:25 PM   #7
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Sounds like I shouldn't worry about it as long as everything else is normal. Just seems weird that other semi displacements cruising nearby don't have the same.
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Old 11-30-2015, 10:46 PM   #8
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Does your boat have a DSS shaft seal, with some of the water going to it as well? These take about 1/3 the water flow out of the exhaust. Have you changed anything else besides the injection elbow?
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Old 12-01-2015, 06:04 AM   #9
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RPR

Given that you are dealing with a potentially failing/plugging heat exchanger and after cooler, the steam may indicate a lower than optimum raw water flow. But as noted, some engine setups are steamers.

On my genset, steam begins to appear when the heat exchanger is slightly plugged, even though the coolant temperature is not increasing.
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Old 12-01-2015, 07:10 AM   #10
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Just seems weird that other semi displacements cruising nearby don't have the same.
Not really. It could be a matter of a few degrees, how the "shower head" disperses the water, how the exhaust run is, etc.
I get steam sometimes depending on conditions.
When you get steam and you're idling, then you have issues (unless you have just throttled down from a hard run).
Or if you suddenly have steam all the time and never did before. Then it's an indication of a potential issue.
My old Perkins would steam in spring and fall, never in the summer (L I Sound).
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Old 12-01-2015, 08:46 AM   #11
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Does your boat have a DSS shaft seal, with some of the water going to it as well? These take about 1/3 the water flow out of the exhaust. Have you changed anything else besides the injection elbow?
Don't think that's correct. Have 2 of those on different boats. The feed line is 3/8". Doubt you could pass 3 GPM through a 3/8" hose.

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Old 12-01-2015, 07:32 PM   #12
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Is 3gph the spec for a t6.354?

(I don't have a dss)
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Old 12-01-2015, 08:22 PM   #13
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Always had a tiny bit of blue and steam on start-up of my Perkins HT6-354 which had 20,000hrs on it (12,000 done by me). All smoke/steam disappeared after a few minutes. Restricted raw water flow would be my first guess.
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Old 12-01-2015, 11:31 PM   #14
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Steamy exhaust

This past summer, we were experiencing an intermittent water flow alarm when running our port FL120 up to 1750 rpm. Also was getting steam whisps from the port exhaust. At 1500 there were no alarms and the steam was minimal. Checking engine temps with an IR showed the port engine running about 20 degrees higher than stbd. Not overheating, but an indication that something was amiss. Next stop I started to methodically go through the raw water system.
Strainer, impeller, hoses, through hulls and heat exchangers were " serviced " by a yard in Tacoma, paid for by the previous owner, while on the hard for bottom paint.Six months before we purchased.
I started at the exhaust elbow, and it was clean. checked each HX and they were clean, impeller good, strainer good, removed each new hose and inspected, all good, up to the through hull which was serviced and not suspect.
The input to the through hull looked good from the inside of the sea chest, the exterior of the through hulls were nice and shiny clean.
After the next days running, same problem!!!
The only thing I didn't take apart was the sea cock, and being in the water and away from a close marina,not something that I wanted to do. The only part of the system that I haven't removed was the bronze elbow coming off the sea cock. Don't ask why.
Hello, what a find! How that engine ran at normal temp at all surprised me.
See the pic. After finding this, I took off the stbd elbow and it was whistle clean. This stuff was like cured concrete, had to chisel it out, it was not soft.

Bill
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Old 12-02-2015, 06:54 AM   #15
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More important than steam in the exhaust is heat in the seawater side of the cooling system.

Use your lazer gun to see if the sea water gets to 140F anywhere in the circuit.

140F is about where salt will come out of suspension and begin to plug whatever its running thru.
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Old 12-02-2015, 07:25 AM   #16
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Is 3gph the spec for a t6.354?

(I don't have a dss)
The spec per the Sherwood pump drawing is 28.5 GPM at 3000 rpm (that would be pump rpm).I don't know what the gear ratio between the engine and pump is.
I will send you the drawing via e mail.
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Old 12-02-2015, 09:50 AM   #17
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Sounds like I shouldn't worry about it as long as everything else is normal. Just seems weird that other semi displacements cruising nearby don't have the same.

Steam is not normal. You hit the nail on the head with noting other boats don't do it. Steam seems like anchors, everyone has a different explanation but if new boats and other boats are not steaming away what is different with yours.

A thorough inspection of the internals of your system is in order to sleep well at night. Not just a flushing.

Look at your system. Is there any point where junk or old impeller pieces could collect?
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Old 12-02-2015, 10:23 AM   #18
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not sure saying that steam signifies a problem is totally accurate...a large percentage of every boat I have ever been on steams a little during the right circumstances.

heck, under the right circumstances, the water you are going through is steaming without going through the engine....

thus the term "steam fog".....
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Old 12-02-2015, 10:39 AM   #19
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Ok perhaps not 100% accurate. Maybe 96% []A few wisps of steam I don't chase, just watch, but the OP has a 40 YO boat that he says has lots of steam. To me that is very likely a problem and only after a full tear down would I be comfortable,
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Old 12-02-2015, 11:00 AM   #20
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Steam is not normal.
That has certainly not been our experience or observation in this region. Steam to varying degrees, from a little to a lot, is very common here particularly in the late fall through early spring and the age or type of boat has nothing to do with it. A blanket statement that steam in the exhaust is not normal is very misleading and would indicate that a huge number of boats in this region have some sort of cooling problem which, of course, is not true.

Steam certainly can be an indication of a cooling issue but it is by no means an automatic indicator of one.
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