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White Smoke

troym

troym

Advanced Contributor
'97 5.7L, Alpha, Gen II., 2bbl Mercarb

What causes white smoke?

About two weeks ago, I ran the boat to the fishing grounds (45 min) at moderate speed (3200rpm), trolled for about 3 hours at 1200-1500rpm, ran back in at 3200rpm. No smoke until I throttled back, entering in the no wake zone. Then noticed the white smoke.

Have been to the boat to run the engine twice since, to keep the batteries fresh. Both time smoked from starting and running at idle, and reving up a little (1500rpm) ...lots of smoke!

Engine seems to be running OK. Starts easy, and idles smooth, no vibrations, unusual noises, etc.

Not losing any coolant or oil.

The fuel is down to the bottom 1/4 of the tank. But stabilizer was added when the tank was last filled, maybe a month ago.
 
Are you sure it is smoke and not condensation?

white smoke is usually a sign of coolant leaking into the combustion chambers.
 
Look at the spark plugs..........for a quick check. If one or more are very clean vs the others than a head gasket.

Is it a closed cooling (with heat exchanger) or raw water (with NO heat exchanger)?
 
troym said:
'97 5.7L, Alpha, Gen II., 2bbl Mercarb

What causes white smoke?

Not losing any coolant or oil.
Click to expand...
You say "not losing any coolant" which would lead us to a Closed Cooling system, correct?
As noted, white smoke is generally water or coolant being heated or combusted.
Since you are closed system cooled, your reservoir level would be diminishing if this was from coolant.
With a good nose, we can generally smell heated Ethylene Glycol that is mixed in with the exhaust.

An exhaust manifold gone bad can introduce sea water into an area where it can be turned into steam.

Loss of cooling water on one side of an exhaust system can also produce steam, but I'd think that you'd see other tell tale signs.
Perhaps check the temperatures between exhaust manifolds.

Keep an eye on your coolant level and on your engine oil.
 
Is this a complete fwc system? Does A/F flow through the exhaust manifolds also? When is the last time you replaced manifolds and risers, when was the last time the raw water pump was serviced. Lack of raw water flow (in or out) will cause a steaming issue.
 
Yes, closed FWC (full... through the manifolds). Risers and manifolds are <1 year old.
Raw water pump is getting pretty old... hmmm. Coolant temp is good though, but I should have thought to check how hot the risers were.
Going to pull the boat out in the next week or so to clean the hull and repaint. Will be a good time to check out the raw water pump.
I'll pull the spark plugs and take a look there too. While the plugs are out, might as well run a compression test just to see if there's anything going on with that.

Thanks
 
troym said:
What causes white smoke?

Have been to the boat to run the engine twice since, to keep the batteries fresh. Both time smoked from starting and running at idle, and reving up a little (1500rpm) ...lots of smoke!
Click to expand...
Does it smoke immediately at start up or when it starts to get warm?
 
So the crankcase is not over full, nor the oil milky ?
You have a fuel water sep. filter ? Dump it in a clear jar let sit see if you see alot of water in the filter.
Do the compression test on a warm motor with all the plugs out and the throttle fully down.
Read the plugs keep track of what plug went in what hole.
Maybe it was just water in the fuel. We will know when you get back to use with the compression numbers.
You can always pressure test the cooling system if you want.
 
Does it smoke immediately at start up or when it starts to get warm?
Click to expand...
...the last two times I ran it, it smoked from starting and never stopped smoking. Ran it for about 20 minutes after it warmed up.

Oil looks fine, a little dirty... an oil change is on the 'to-do' list.
Dumping the fuel from the separator into a glass jar is a good idea, will do that. Since the tank is getting lower than I normally keep it anyway, would be a good time to drain it, open it up and wipe it out. To my knowledge, that's never been done before. 15 years worth of corruption building up in there could be a contributing factor, especially considering the last 7 or 8 years we've been forced to use 10% ethanol.
 
White smoke is water plain and simple, you know that also. The weird part is the smoke doesn't stop. We will know more when the plugs come out, and if they all look steamed clean.
 
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