Exhaust Steam

Bill Gillespie

Bill Gillespie

Member
Apr 20, 2007
222
Danville, CA
Boat Info
2006 44 Sundancer
Engines
Cummins QS5
I have twin 7.4 EFIs in my 97 Dancer. The port engine had steam evident at 3400 RPM, deteriorating to as low as 3000 RPM with a slight increase in temperature (perhaps 170 where 160 is normal) I had the water pumps serviced and impellers replaced (the port impleller blades had collapsed). Now there is a small amount of steam at 3400 RPM and a very slight increase in temperture. Marinemax says this is normal and they are surprised that both engines do not behave like this. Another mechanic and an engineer think it is significant. This boat was in salt for 8 years and now is in fresh water. This has been the subject of many threads. Any thoughts or leads?

Thanks,

Bill
 
Bill,

I have a 92, 370 Express with Merc 454's. Both my engines steam under load (3100 RPM's). I have been told this is normal, also here on the Chesapeake Bay I've noticed numerous other boats doing the same. Keep an eye on your temp.

Mike
 
Mike said:
Bill,

I have a 92, 370 Express with Merc 454's. Both my engines steam under load (3100 RPM's). I have been told this is normal, also here on the Chesapeake Bay I've noticed numerous other boats doing the same. Keep an eye on your temp.

Mike
Click to expand...
It's normal ... at least with lift mufflers. the hot exhaust gases evaprate some water that codenses when exhausted ... even in 90F weather ... both of mine do it
 
Same problem here with steam. .....callled my mechanic today....he said it my just be that the water (raw) temp is still cold and hitting the hot riseres makes steam.......but will check and see if any hoses are clogged.

My water temp gauges were at 165 degrees and it was only the starboard motor.....don't get it .
 
See all my other posts.
When you are steaming at idle, that's an issue. Probably not enough water getting through. Scoops (barnacles), strainers, hoses, impeller, coolers (oil, fuel) and heat exchanger.

When you're whisping at speed, be a little nervous, but just watch the temp gauges.
 
Bill,

Did you get any other responses regarding this? I would be curious to know, I have consistently had steam from both engines since I owned the boat. It trails 3 to 4 feet behind the boat at 3000 RPMs. I also consistently check my oil, coolant, etc so don't believe it is a head gasket. I hope it's normal!!
 
The consensus among the experts, Sea Ray mechanics and two mechanics that I trust, a little steam under load is normal. It is caused by heated manifolds evaporating some of the water. The universal advise is to watch the temperature guage, as that is the critical factor.

Bill
 
Bill Gillespie said:
The consensus among the experts, Sea Ray mechanics and two mechanics that I trust, a little steam under load is normal. It is caused by heated manifolds evaporating some of the water. The universal advise is to watch the temperature guage, as that is the critical factor.

Bill
Click to expand...
I don't believe that the evaporation takes place in the manifolds since the waterflow is still solid there and not mixed with gases. It is the hot exhaust gases hitting the alerady heated water in the elbows and lift mufflers where the water evaporation takes place, creating the steam you see.
 
Steam Is Normal

Before my current boat, I had a 1996/370 with Mercs, and their was always some steam vapor out of the bypass once we got to operating temp, and then many years ago I had a Cris Craft with a Grey Marine which always had some steam.

Steam just comes with gas engines
 
I had three Inboard boats with big block gas engines. A 1993 330DA with carbed 7.4's, a 1998 330DA with MPI 7.4's and a 2002 380DA with MPI 8.1's.

The 1993 had lift mufflers with side exhaust (wow...just had a flash back to my '66 vette) and the 2002 had the lift mufflers with underwater exhaust with the side tell tales. The 1998 did NOT have lift mufflers, as it had the Sea Ray Log exhaust with underwater exhaust and the side tell tales.


ALL three boats produced steam at cruise.
 
how exactly do you know if you're blowing steam or burning a bit of oil (other than constantly checking the dipstick)? white smoke is steam, blue would be oil? i've noticed more white wispy smoke running in the cooler weather we've had of late here in NJ. will that diminish as the weather and water warm up??
 
Smoke from oil is really smoke.

Steam vapor is water vapor and in addition to its white color, it is also different in that it is lighter and dissapates more quickly since it just dissapears into the ambient air. The odor of the 2 is also completely different.

You might think the difference is subtle until you see both and know which is which.

Since you don't use capitals and end every sentence with a question mark, I don't know if you asked a question or if I answered one.............
 
hi frank:
3 of the 4 sentences above were questions, which is why they were ended with "?" the one that ended with a period was a statement. i've been spoiled by MS word, which puts caps in automatically at the start of sentences, so i've stopped interrupting my streams of consciousness and just skip them all-together. and you have, as usual, answered my (grammatically incorrect) questions most adequately, thank you very much! (---> explanation point here implies pleasure and a light-hearted nature to my tone, as does the forthcoming "smiley" emoticon) :grin:
 
Hello People,

you said one off the impellers has lost a few vanes maybe these vanes are blokking water hoses.
check the 2 small hoses fron thermostat housing to exhaust manifold.
or maybe there is a vane stuck in the housing itself
good luck dancer340
 
You must log in or register to reply here.

Forum statistics

Threads
113,194
Messages
1,428,285
Members
61,103
Latest member
Navymustng
Back
Top