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White smoke out of the exhaust on a 1990 454 Crusader with quadrajet carb

C

contender31

Regular Contributor
Hello I have white smoke on start and idle on my crusader 454 - the engine starts on demand, idles properly and riuns at cruise speed normal. When starting it smells of gas combined with a small discharge out of the exhaust port. I don't smell gas in the engine compartment but do smell gas as if it is burning slightly rich. When I take off the carb arrestor I did notice black dirt like subtance on top of the carb. Hopefully this is enough info to get an intelligent suggestion or solution. Does the carb need adjustment?
Note : being in Florida we run our boats all year so it isnt winter stored.

Thanks in advance
Gary
 
Excess gas (overly richn) does not normally produce white smoke: coolant leaking into the motor does. I suggest a careful compression test to see if you have a problem.

Good luck,

Jeff
 
Gary,

I can only relay some details about the same series of events we had about 5 years ago. The smoke was white with a very slight blue mixed in. The boat had been neglected when we bought it so I trusted nothing to be in proper working order. The carbs were changed from the Carter to the Edelbrock. I could swear the only difference looks to be the nameplate on the priliminary inspection.

I took the old Carters apart and cleaned and used the rebuild kit except for the bushings in some linkages and the butterfly. Some parts were clearly worn or rubbed heavily. It has been 5 operating seasons here in NJ and the startup are much "cleaner"...I still pump the $#!T out of the throttles after a week or more of sitting and that sometimes causes a blue/white puff on startup but it is only that which will emulate the issues of a smokey, rich smelling starting exhaust.

Once out and running, fishing, starting 20 times drift fishing etc....no problem. We also had some valve seal issues but that was corrected during the valve jobs on all 4 heads. Oil leakdown caused a little smoke at that time as well. It was the carb change or rebuild that made most of the improvements

Do you have a log history ( or any history ) on the carbs
 
I rebuilt the carb last year and it ran without incident. I do have some brownish sludge on top of the louvers in the carb. Building guy here not sure if the wording is correct on louver?:) Perhaps I need to run the boat at a higher rpm and see if it continues??

Thanks for the reply


knuckle47 said:
Gary,

I can only relay some details about the same series of events we had about 5 years ago. The smoke was white with a very slight blue mixed in. The boat had been neglected when we bought it so I trusted nothing to be in proper working order. The carbs were changed from the Carter to the Edelbrock. I could swear the only difference looks to be the nameplate on the priliminary inspection.

I took the old Carters apart and cleaned and used the rebuild kit except for the bushings in some linkages and the butterfly. Some parts were clearly worn or rubbed heavily. It has been 5 operating seasons here in NJ and the startup are much "cleaner"...I still pump the $#!T out of the throttles after a week or more of sitting and that sometimes causes a blue/white puff on startup but it is only that which will emulate the issues of a smokey, rich smelling starting exhaust.

Once out and running, fishing, starting 20 times drift fishing etc....no problem. We also had some valve seal issues but that was corrected during the valve jobs on all 4 heads. Oil leakdown caused a little smoke at that time as well. It was the carb change or rebuild that made most of the improvements

Do you have a log history ( or any history ) on the carbs
Click to expand...
 
Smoke or Steam??? in other words, can you "see thru the cloud"?

2X jeff's thought - coolant burning = white smoke....a 'steaming' condition can be due to lack of raw water flow thru one or more exhaust elbows....measure them with an IR gun if available - one hot elbow should be self evident.

The "black stuff" under the flame arrestor isn't unusual - byproducts from the gasoline evaporating. Also, sadly, it isn't unusual for a Q-jet to run 'rich' at idle speed, especially on a big block. Easy to fix but somewhat time consuming.
 
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Thanks - raw water flow great elbows easy to touch by hand and new raw water pump working great.

Any idea on an easy adjustment to set the carb?

Thanks

makomark said:
Smoke or Steam??? in other words, can you "see thru the cloud"?

2X jeff's thought - coolant burning = white smoke....a 'steaming' condition can be due to lack of raw water flow thru one or more exhaust elbows....measure them with an IR gun if available - one hot elbow should be self evident.

The "black stuff" under the flame arrestor isn't unusual - byproducts from the gasoline evaporating. Also, sadly, it isn't unusual for a Q-jet to run 'rich' at idle speed, especially on a big block. Easy to fix but somewhat time consuming.
Click to expand...
 
You can only adjust them for idle conditions. I use a vacuum gage to get best vacuum highest readings) since it's surprisingly difficult to do it otherwise. Unlike a car engine, with its flexible motor mounts, a marine engine just sits there if it's idling poorly. A car engine, by comparison, would rock back and forth, indicating poor idle mixture.

Finally, be careful WHERE you get a vacuum signal; using the convenient PCV valve hose will produce an incorrect mixture (way too lean). The PCV system sucks in air at idle speeds (unless blocked off by a vacuum gage! Think about it.)

Jeff
 
You can make a helluva lot more than just idle adjustments on a q-jet!

Few, if any, crusader blocks have PCV so that isn't an issue.

If the idle mixture screws don't have any control, lower the idle speed. If they still don't have any control, you need to see if the transfer port is covered or exposed. If the latter, time to add some air - if the former, time to clean the idle system.
 
..."You can make a helluva lot more than just idle adjustments on a q-jet!"

Obviously, I meant with a screw driver while the motor is running!

Jeff
 
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