1996 Volvo 7.4GL smokes alot during start up

danyus1

Cadet
Joined
May 8, 2017
Messages
12
We have a 1996 Volvo 7.4GL Carb, when we start it up I notice it smokes quite a bit. I don't notice it as much while underway, but anytime it's at an idle it smokes quite a bit. Is there anything I can look for or add to the oil/gas to limit this, or is this a bad sign of things to come. It starts right up and has no shortage of power. It just makes everyone at the dock and our cabin smell like exhaust. I talked with someone else about it and they mentioned it's a big block carb most run rich and it is what it is, but I'll like a second or third opinion on the matter. Thanks everyone!!!
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,306
first, you have to determine is it smoking because of oil leaking past the valve seals (blue puff when you start) or is it running rich

if its running rich, properly addressing the carb will take care of it.

post your complete model number so we can dial into the correct carb that is on it.
 

danyus1

Cadet
Joined
May 8, 2017
Messages
12
Ok, Ill try to get some pics and find the model plate and post it this week. Thanks!
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,093
black smelly exaust is most likely a choke plate set too tight.
 

danyus1

Cadet
Joined
May 8, 2017
Messages
12
I couldn't make out any numbers on the lab sticker. I've attached some pics of the motor and carb. The exhaust fumes are pretty strong and I always have a black residue that builds up on the back of the swim deck each year. It appears to have an electric choke on the carb. Is this something that can still be adjusted? I'm usually pretty handy and can do many repair/adjustments myself, but I'm certainly not a carb guy!
 

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Lou C

Supreme Mariner
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Nov 10, 2002
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11,802
Looks like a Holley 4160 4bbl. Go on Holley's website, there is a lot of information there and manuals you can print out. Try leaving the ignition on for a while and watch the choke plate. It should open up because it's an electric choke. If it does not, the heater element may be defective or the wiring to it is. The other thing that can cause this problem, is a faulty vaccum break diaphragm. This is supposed to pull the choke open a fraction of an inch right after it starts, to give it enough air to keep it running. You can watch the choke plate as someone starts it to see if this is working. With a cold engine it should close all the way, as it is in the pic. When it starts, it should open a fraction of an inch. Then as the engine warms up, it should open full vertical. If all that is OK and you still have this problem, then the carb could be set too rich or the float/needle valve could be allowing the engine to flood at idle. They also have a free tech line you can call on the Holley website.
 
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