thru hull exhaust water vapor

[krisnowicki]

My boat now has about 7 hours on it. I am still getting water vapor out of the exhaust. IT is not hot and is not smoke it disapates very fast. At idle it only comes from on side ( the same side that the riser is a little hotter to the touch) at around 3000 rpms it comes from both. Is this normal.... It is starting to get colder down here and it only happens when then engine is fully warm. Not at first start up. The engine is new, compression is great all around, and so are all exhaust components. There no water leaking at all and the oil is pristine.

Just worried that I am doing something that will ruin my new engine.

 

[zbnutcase]

Re: thru hull exhaust water vapor

If the engine isn't running hot I wouldnt worry about it. More than likely just due to climate conditions

 

[Fireman431]

Re: thru hull exhaust water vapor

My dual through hull exhausts have always given off water vapor/steam. The degree at which you see it will vary due to the ambient air temp, relative humidity, temp of the water at which the boat is in, and volume of water being moved through the engine (RPM). If the boat is running fine and all gauges are within normal limits, it's probably normal. You only have 7 hours on it, and that's not enough to learn all of the little idiosyncracies of your vessel. Monitor the gauges and go from there.

 

[deves3000gt]

Re: thru hull exhaust water vapor

I have a 350 with dule though hull exhaust and mine does the same thing. once it is warm and idling i get steam from one side and once you rev up a bit it will come from both sides. I would bet if you were on muff you will also find that you have more water coming out of one side then the other at idle, also normal. i have also noticed that if i idle after a hard run i will get more steam.

 

[krisnowicki]

Re: thru hull exhaust water vapor

I figured it was normal. espicially for people with thru hulls.

Thanks everyone

 

[Fun Times]

Re: thru hull exhaust water vapor

Engine Blows Steam Out the Exhaust!!!

Steam appears as billowy white smoke that disappears and has low odor. If the white smoke has a strong fuel smell it might be excess fuel burning and not really steam.

Steam is usually noticed on boats that have direct exhaust. Boats with through-prop exhaust can steam too but it would only be evident if the boat were not in the water.

A little steam is normal. All exhaust will show a little steam now and then especially on cold mornings. If you get excessive steam it may indicate a problem.

Two basic things can cause too much steam.

1. Overheating
2. Leaking Exhaust Manifolds, Risers or Gaskets

1. Overheating causes the exiting exhaust water to turn into steam. A bad Water Pump, a plugged exhaust manifold or elbow or even a bad thermostat can cause the engine to run hot and steam.

2. Old exhaust manifolds and exhaust elbows can get plugged with rust or the can develop internal water leaks. If the xhaust is bad to the point that it is causing steam, they should be replaced ASAP. Bad exhaust will ruin a perfectly good engine.

 

[wca_tim]

Re: thru hull exhaust water vapor

Mine blows a lot of steam out (aftermarket manifolds and long stainless risers, through hull coming out above the rub rails).

even when it is just warmed up it makes a good bit of steam, but it's almost all steam after throttling down after a hard run... nothing is overheating and waterflow is good. engine temp is in good shape, oil pressure within normal limits.

If everything checks out, steam should be fine - especially with throuhg hull exhaust.

 

[tfret]

Re: thru hull exhaust water vapor

Engine Blows Steam Out the Exhaust!!!

Steam appears as billowy white smoke that disappears and has low odor. If the white smoke has a strong fuel smell it might be excess fuel burning and not really steam.

Steam is usually noticed on boats that have direct exhaust. Boats with through-prop exhaust can steam too but it would only be evident if the boat were not in the water.

A little steam is normal. All exhaust will show a little steam now and then especially on cold mornings. If you get excessive steam it may indicate a problem.

Two basic things can cause too much steam.

1. Overheating
2. Leaking Exhaust Manifolds, Risers or Gaskets

1. Overheating causes the exiting exhaust water to turn into steam. A bad Water Pump, a plugged exhaust manifold or elbow or even a bad thermostat can cause the engine to run hot and steam.

2. Old exhaust manifolds and exhaust elbows can get plugged with rust or the can develop internal water leaks. If the xhaust is bad to the point that it is causing steam, they should be replaced ASAP. Bad exhaust will ruin a perfectly good engine.

Boat Tech, I've got an older 5.7L thru hull that steams a lot. Help me understand how a failing exhaust will cause engine failure, and what I need to check to prevent it. Thanks.

 

[Philster]

Re: thru hull exhaust water vapor

Failing (leaking internally) exhaust (metal parts and gaskets) allows water to enter exhaust at wrong point, which can then be sucked back into the engine because on the exhaust stroke, there is a moment when the engine can actually suck water back (reversion). Depending on the cam timing, it can actually be a pretty good valve overlap moment that sucks back fairly strong.

Tiny bits of water are either burned in the exhaust and steamed away and/or condense as droplets which go back to the engine. Some super tiny am't can be burned by the plugs and affect performance -- sometime noticeable and sometimes not.

However, getting moisture into combustion chamber will slowly rust it, or it could build up beyond a teensy tiny am't and seize the engine, blow a rod and pretty much cost you the whole engine. Water cannot be compressed very much (darn near zero), so the hydraulic action puts the smack down on the engine.

You can check the plugs for signs of water. Note: None of this affects the oil.