F70 blowing steam

[Tommyknockers]

Hi, looking for a bit of help.
I have a 2015 F70 outboard, it has about 250 hours use, I have only had it for a month or two so don't know it's history. The engine seems to run perfectly and appears very clean. I have just changed the oil, fuel filters, water impeller etc. I have it on a 21ft boat and it goes perfectly, however, when idling and at lower revs there is steam coming from the exhaust ports. It's definitely not oil smoke, it's steam. The coolant tell tale is very strong, everything seems perfect apart from the steam. Is this normal? I'm confused as it appears water is somehow getting into the exhaust system and vaporised. The engine oil it's self is still ****en in colour, I'm using fresh quality fuel as well. Any ideas?

[ausnoelm]

Still under warranty??

[robert graham]

Steam/smoke coming out of the exhaust is fairly normal....I'm doubtful you have a problem.....

[Tommyknockers]

Sorry it's a 2014 model, not 2015. Typing error. I just can't work out how water gets into the exhaust system to then be turned into steam

[robert graham]

The lower unit/ propeller area is water cooled....the exhaust runs down and out through the prop and without water the prop overheats and melts the center rubber bushing....now that's what I've read and it makes sense to me....

[Tommyknockers]

The main exhaust ports are about 6 inches under the engine cowel, above the water line. The steam is coming out these ports, not the port that ties in with the prop output. I'm not sure how steam can be produced and put out these ports

[99yam40]

have you ever looked at a car or truck exhaust pipe while it is idling?
there is steam coming out of those also, it is a product of combustion of the fuel.
Now if you pull the plugs and see water on them, then you need to be worrying about water in cylinders.
Just an opinion, but I do not know if that 4 stroke has anything like the 2 strokes with exhaust cooling plates

O yea, the idle relief ports are up where you are talking about, they help relieve the back pressure on the exhaust while motor is idling but the main exhaust is through the prop area at higher RPMs

[rodbolt17]

dude
think
your cooling the exhaust and the oil with cold water.
it will steam a bit, more so after a run then returned to idle.
if the alarm system works and your not getting one.
run it.
mostly its more like fog, not hot like actual steam.

[99yam40]

Rod if you do make the move south I hope you will still check in on us after you are settled

[zenoahphobic]

dude
think
your cooling the exhaust and the oil with cold water.
it will steam a bit, more so after a run then returned to idle.
if the alarm system works and your not getting one.
run it.
mostly its more like fog, not hot like actual steam.

Yeah, could still happen when engine stopped for a while. No more cooling but heat stored in metal of engine, warms the little cooling water left, it vapours and expands oozing out those ports. Fog or steam? depends how precisely you were taught at school, nice illustration/description though.

OP, what you actually see as opposed to what is actually there, is entirely dependant on air temperature, humidity and elevation (pressure). More "steam" (water, the product of combustion) is seen when cold and/or very humid.

[Tommyknockers]

Thanks for the replies, I had read a head gasket might be blown and got a bit worried, however there is no more symptoms I'm happy now it's just steam/fog being emitted from the water cooling the exhaust etc.
Cheers

[rodbolt17]

actually, it is called an idle relief.

yep it tends to "steam" but if you catch a bit in your hand you will note its not steam.

steam by a quirky law of thermodynamics must be above about 212*F at se*****l or its water.

fog or other condensates can actually be cooler.

[Tommyknockers]

Chaps let's not get hung up on exact definitions etc, its white cloudy stuff which I believe to be from water and looks like steam coming out the ports just under the cowel. So the general opinion is that it's pretty normal then? Was out for a few hours today and it's still steaming a bit however it runs fine

[rodbolt17]

put your hand back there and feel it.\
if its really hot you may have an issue.
most likely its not and its normal.
kinda like on a frosty day you can see your breath.
is that steam or condensation?

[zenoahphobic]

actually, it is called an idle relief.

yep it tends to "steam" but if you catch a bit in your hand you will note its not steam.

steam by a quirky law of thermodynamics must be above about 212*F at se*****l or its water.

fog or other condensates can actually be cooler.

Yep again.

Actually we agree it is water; that it is a product of combustion, that by definition occurred at very high temperatures (far greater than 212F though).

Interestingly, the water was never made as a liquid but as a colourless gas, it was when it was cooled enough that we actually see it in it's liquid form, albeit as "fog" or condensate. It may well then be reheated and converted to "steam". Two processes going on!

Fog is water coming out of the air, and steam is water going into the air - but these are just terms we attribute to what we see. Of course water, most water goes into the atmosphere invisibly, and most notably comes out as rain or directly wetting surfaces (dew without fog).