White steam

DarrenC

DarrenC

Member
Jul 10, 2018
164
Boat Info
2001 Sea Ray Sedan Bridge 400
Engines
Mercruiser horizons 350
Im getting some white steam it appears out if my exhaust while under load around 3,500 rpm. Just noticed for first time yesterday. Is this normal? I’m thinking it has probably always done this but I’ve never noticed because I usually have my canvas down. Just checking.. Thank you in advance.
 
DarrenC said:
Im getting some white steam it appears out if my exhaust while under load around 3,500 rpm. Just noticed for first time yesterday. Is this normal? I’m thinking it has probably always done this but I’ve never noticed because I usually have my canvas down. Just checking.. Thank you in advance.
Click to expand...
White steam is usually water burning in the combustion chamber.
Probably good idea to not run the motor until you figure out where it’s coming from.
Are you in saltwater? How old are your manifolds and risers?
 
IMG_4230.JPG
Completely normal to see it in your exhaust. Lighting conditions make it more visible at some times, and not so visible at other times. Don't worry about it.
 
JVM225 said:
White steam is usually water burning in the combustion chamber.
Probably good idea to not run the motor until you figure out where it’s coming from.
Are you in saltwater? How old are your manifolds and risers?
Click to expand...
I’m in salt water.
 
Remove your spark plugs and see if there is water or rust present.

I see some inboards that have been steaming out the exhaust for years and some that don’t. Mine don’t.

I can be an indicator of trouble, but apparently not always.
 
I just put new plugs in 3 days ago. Also it was about 62 degrees at night last night when I noticed. Only did it under load. Not slow speed so maybe I could be jumping gun. Air may have been cooler then exhaust.
 
DarrenC said:
I’m in salt water.[/QUOTE

Where are you located. If the sea water and air is cold it will produce white exhaust steam which is perfectly normal. If your engine temps are normal and you are not loosing coolant you are fine.
Click to expand...
 
scoflaw said:
partially plugged manifolds and risers will do that
Click to expand...

Definitely. An IR thermometer would help here.

If these parts of the exhaust system are hot, they’ll boil water on it’s way out.

At 62 degrees ambient temp, seeing steam makes some sense though. Cars steam out the exhaust in cold weather.
 
Our 320 had steam on the old and new elbows on our freshwater cooled motors. Was more obvious earlier and later in the season.
 
DarrenC said:
I’m in salt water.
Click to expand...

Is this something new?
You indicated that it only did it under load.
It’s possible that you can see some steam when you first start a boat when the air and water are cold but you say it happened under load.
When was the last time your exhaust was changed?
Always helps if you put your location in your profile.
 
DarrenC said:
Im getting some white steam it appears out if my exhaust while under load around 3,500 rpm. Just noticed for first time yesterday. Is this normal? I’m thinking it has probably always done this but I’ve never noticed because I usually have my canvas down. Just checking.. Thank you in advance.
Click to expand...

My 360DA w/ 8.1 produce steam ALWAYS. New or old manifolds and elbows, no difference. I get more steam when the water and air temps are a little cooler. I have Smartcraft Vessel View and can monitor my temps and I am not over heating.

Last year port motor was showing elevated temps (near 180) and found a couple of broken impeller vanes in the transmission cooler inlet. Replaced the impeller, found all broken vanes, engines back down in the mid 160's (temp wise), still steams. Those manifolds get pretty hot right at the exhaust ports from the cylinder heads and need the cooling water to carry the heat away.

Sorry, kinda long winded. You should be able to touch the manifolds and elbow / risers without getting burned. You may want to try checking the temps while running with an IR thermometer sensor.
 
JVM225 said:
Is this something new?
You indicated that it only did it under load.
It’s possible that you can see some steam when you first start a boat when the air and water are cold but you say it happened under load.
When was the last time your exhaust was changed?
Always helps if you put your location in your profile.
Click to expand...
I’m located off cape cod Ma where water temps are very cool and again only 59 degrees again today. I only noticed it other evening when I went for a ride where sun wasn’t out and it was around 61 degrees out. Doesn’t do it at idle.
 
I have twin 8.1s in my monticello HB and she always blows steam, when loaded! All the temps are within normal range so I havnt really worried about it, i do keep an eye on the temp gauges just to make sure!
 
My 7.4's have steam out of the exhaust almost always. The colder the lake water and air temp the more it's noticeable.
I am by no means a mechanic though.
 
Last edited:
Ezsteps said:
My 7.4's have steam out of the exhaust almost always. The colder the lake water and air temp the more it's noticeable.
I am by no means a mechanic though.
Click to expand...

+1.... My 8.1's do it and my 5.7's on my old boat did it too....
 
Steam can be very Normal when the water temps are low. Watch my signature video...
 
It has more to do with the dewpoint when It’s close to the air temperature the exhaust doesn’t evaporate as fast so it looks like a lot more steam is coming out but it’s just not dissipating as fast ,nothing to worry about check the local weather station for the area that you’re in on that day and confirm the dewpoint and temperature if they are close together you can confirm this
 
DarrenC said:
I’m located off cape cod Ma where water temps are very cool and again only 59 degrees again today. I only noticed it other evening when I went for a ride where sun wasn’t out and it was around 61 degrees out. Doesn’t do it at idle.
Click to expand...

I get that the water and ambient temps can contribute to the appearance of steam, but if it were me I would be a bit concerned that as you say it doesn’t happen at idle, but only under load.
Depending on the answers to the following questions I may want to take a little bit more of an in depth look if it were my boat.
1. Is this steam something new?
2. What does your gauge say you’re temp is when the steam appears?
3. How old are your manifolds and risers?
4. What did the old plugs you replaced a few days ago look like?
 
You must log in or register to reply here.

Forum statistics

Threads
113,116
Messages
1,426,393
Members
61,028
Latest member
ddbyrd329
Back
Top