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dchatagnon
09-20-2006, 04:40 PM
I'm having some litlle black smoke when I start the boat first time of the day. (cold engine)
I guess it's a carb issue. Engine too rich?
I have to adjust the air/mixture of the carb?
what should be the choke adjustment position? (90, +45 or -45)
It's just a 1 year old holley 4160 carb.

Thanks for your help.

michael freeman
09-20-2006, 04:50 PM
Could be the valve guides are a little warn. Oil is getting past after sitting and causing the smoke on start up. It should go away after 5-10 seconds tops.

My understanding is this isn't a big problem.

dchatagnon
09-20-2006, 04:58 PM
I have installed two new GT40 heads in July. so the valves should be ok.

NeilM
09-20-2006, 05:19 PM
Black smoke = running rich, which is common at startup. Cold engines require a richer mixture. The only way to determine if it's "too rich" is to back off the choke a bit at a time. If it starts to falter, then it's not rich enough.

Jwhitsett1129
09-20-2006, 05:27 PM
How do you adjust the mixture on one of these carbs?

east tx skier
09-20-2006, 05:36 PM
Check out skidim's maintenance FAQ (http://www.skidim.com/Faq_Maint.asp#HOLLY%20CARB%20ADJUSTMENT%20INSTRUCT IONS). Good stuff in there.

rcnjson
09-20-2006, 05:37 PM
Black smoke too rich or too fat or too much fuel or not enough air, however you want to look at it. White smoke is oil, could be the valve seals or other issues. If the black smoke goes away, after a short while, it is the choke because the choke will open as the engine warms up and allow more air thus leaning out the mixture. If the black smoke is always a problem at idle, you can adjust the idle with the idle mixture screws (at the base of the carb). If the black smoke is always there ie. at all throttle positions, it is the jet size, more specifically the jets are too big. Hope this helps.
k

dchatagnon
09-21-2006, 02:59 AM
Ok. Thanks for all your answers. The black smoke goes away after a short while. So, I assume it is the choke. I will have a look on it and back off the shoke a bit.

edwinfuqua
09-21-2006, 03:36 AM
Ok. Thanks for all your answers. The black smoke goes away after a short while. So, I assume it is the choke. I will have a look on it and back off the shoke a bit.
I don't have a 'choke' on my ride. I just pump the throdle a few times to squirt gas in the intake then set it at about 1/8 throdle, turn the key and start.

When I had black smoke on start it was because I had an exaust leak and the engine was eating more exaust than fresh air. Worst case is you might foul your plugs. You should not have to choke an engine on start up in 75+ degrees temp. But you have a newer boat than me. I'm an old timer.

Edwin

TRBenj
09-21-2006, 08:35 AM
I don't have a 'choke' on my ride. I just pump the throdle a few times to squirt gas in the intake then set it at about 1/8 throdle, turn the key and start.


Are you sure? The Holley's Ive seen have an electric choke. Most carb'd boats still need a small pump of the throttle to start when cold, though.

wesgardner
09-21-2006, 12:12 PM
I've got my choke purposely "wired open" during the summer as it was choking too much upon start...

tdaines@hotmail.com
09-21-2006, 10:45 PM
A couple of thoughts:

First, when you change the airflow of an engine, you have to change the way the engine receives air/fuel. GT40 heads are quite different than the stock heads you had on that motor, and they can move way more air through.

Second, once you've increased your air-flow, when the carb auto-chokes at cold-start, it will pull a lot more fuel in (or a much higher fuel-air ratio) creating your black smoke. Ironically, you're probably running a bit too lean once the choke opens!

The lesson here is that anytime you mess around with engine dynamics, it creates a domino effect of necessary tuning. Your cam is probably not right for the heads now, and the carb tuning is going to be way off. The net result of your expensive head change = less HP, poor mileage, and yes - black smoke on cold startup. A lot of engineers spent a lot of time figuring out a combo that was optimized (not maximized!) for the application. The heads matched the cam, which matches the spark, and air/fuel mixture. Everything works in concert.

I'd take your boat to a good (marine authorized) tuning shop, and have them help you re-jet your carb (absolutely do NOT try putting an automotive carb on!), and think about updating the cam at the same time.

Good luck - I do love getting every little bit of power out of these babies, but it's going to be an expensive journey!

dchatagnon
09-22-2006, 07:41 AM
ok Guys.
I have adjusted the choke and I have checked with the engine cold ...and no smoke anymore!!!

FYI:
I have replaced the heads with the original ones. The boat already came from the factory with GT40 heads. (1993 PS 190)
So no need to wonder if the cam is optimized or not for the GT40's .Then, the carb is new also and it's a Holley 4160. Everything has been checked and changed last winter: wires, new electronic ignition module, new coil.

The boat runs now like a champ and my philosophy is to keep it with the OEM original parts.

Damien.

tdaines@hotmail.com
09-25-2006, 07:57 AM
Awesome!. Congrats - sounds like you did the right thing all around - happy skiing...

TIM

dchatagnon
09-25-2006, 02:09 PM
Thanks man! Happy skiing to you too!