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seano
06-30-2000, 07:25 AM
I've just installed a new set of 350 Mag MPIs in my 28 Cigarette and they have less than 10 hour on them. The boat had been sitting for about 5 years and I pumped the tanks and put fresh fuel in (93 octane). After running the boat about 3 hours, i noticed alot of black soot on the transom and cleaned it off. I fugured, maybe I hadn't gotten all of the old fuel out of the boat and that was causing the motors to run rich. Now I have run through 100 gallons of fresh fuel and still the soot...why is this---these motors are fuel injected---are there is a fuel air mixture adjustments, etc?

GeneD
06-30-2000, 08:40 AM
Hey, I've got a relatively new engine also, (carburated) and I have gotten soot on the transom since day one. It seems to be part of boating with thru hull exhaust.

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GeneD
007
Melbourne, Florida

Jamesbon
06-30-2000, 09:41 AM
Out of the two carburated engines which have lived in my beast, both "painted" the transom black after time. (just gotta scrub her every few runs)

RickSE
06-30-2000, 09:45 AM
Same here, I've had a constant problem with soot on my carbureted 96. I've always attributed it to running at high altitude. I've been able to minimize it though by rejetting the carb. One thing I've noticed on carbureted marine SBC's is that #8 & #6 cylinders always seem to run rich. I would think that a MPI engine would be immune to this though, since they typically run lean and have better fuel control.

Peter Beck
06-30-2000, 10:41 AM
My 98 22 does the same thing.

CDMA
06-30-2000, 12:29 PM
That is funny I have never gotten any soot on my transom...oh wait my boat doesn't run.

Chris

GEOO
06-30-2000, 12:43 PM
I wish I had soot on my transom like last year!! The faster you go the more soot you'll get?? More back draft?? GEOO

Scott Pearson
06-30-2000, 01:27 PM
Guys stop your crying! Paint/Undercoat the transom black and be done with it!


Kidding!


(NJ) Scott

seano
06-30-2000, 02:07 PM
Geoo------I like your response the best! I never imagined that soot on the transom was something that is "normal"---especially on a fuel injected engine. You guys actually live with this??? I'm used to outboards and thought I was done with smoke and soot...at least I got rid of that annoying blue smoke! http://206.150.187.82/ubb/smile.gif

Frank Civitano
06-30-2000, 02:09 PM
If your engine is running at top eff, You will get soot on the rear of your boat. Also if your running cooler you will get soot(no thermastat). My supercharger made my rear of my boat look like I need a chimeny sweeper every time I get done. But now I hall a@#

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Frank Civitano

Stromer
07-01-2000, 09:15 PM
I have a new 5.7GM EFI that produces the same soot you are experiencing. I have learned to deal with it. Purchase some "Spray Nine" cleaner - it works great at removing the soot.

RickR,GroveCity
07-02-2000, 10:38 AM
Stromer
What is spray nine?
Does it remove the wax also?

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RickR mailto:riggerb@aol.comriggerb@aol.com</A>

FASTEDDIE
07-02-2000, 12:06 PM
Rick,
Spray nine is made in New York state,Stomers
original homesite. Its a high PH degreaser and yes it will also strip wax. Any chemical that attacks grease and oil will also soften or remove wax.We had a couple of our Donzi troops make an interesting observation and I'll pass it on but I can't verify it. They also had soot on the transoms running thru the hull exhausts on 502's but changed from regular motor oil to Mobil One and saw a noticable lessening of transom soot.If anyone wants this type product in concentrate ,go to your local janitorial supply house and order one gallon of any cleaner that contains butylcellosolve. You should be able to mix one gallon of concentrate and make 20 gallons of usuable cleaner. Also great for cleaning bilges and spray on vinyl seats FYI

FASTEDDIE


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FASTEDDIE

Gearhead99
07-02-2000, 05:47 PM
Soot on the transom is part of high performance, through the transom exhaust.

Make sure that your engine isn't running too cold. The injection will richen up, like a choke. How do the plugs look???

Lots of cleaner and wax.

Barry Phillips
07-11-2000, 07:49 AM
I have the same problem on my 18, I use
Sonax a German product on my cars
and boat. My local speedshop dose
not always have it so now I mailorder
it by the case. This is a great product
dose not take off wax and leaves a film
on glass to bead off water, like RainX.
I clean the transom with it every time
use the boat no problem no stains.
SO-SLO

seano
07-11-2000, 08:18 AM
thanks for all the advice---I' guess I'll just have to deal with it---better rich than lean, huh? I used GreezOff---works like a champ!

Tselby
07-11-2000, 03:20 PM
I may be wrong but an MPI is a closed system and has no means of compensating for outside air temp changes. Unlike a carburated system you can tweak on the fuel mixture, with the MPI you cant. Neither can you add all the little hotrod parts to an MPI either. On warmer days the soot probably increases and on a cool day, I bet its less. Its the nature of the beast. You got to live with it.

Tselby
18 2+3
Charlotte,NC

GEOO
07-11-2000, 04:24 PM
Tselby, Most MPI's have an air temp probe and adjust for the air temp. Some of the better MPI run in "Closed Loop" mode. I was always confused by this, but a "Close Looped" system uses O2 sensor and corrects the air fuel mixture to a programable ratio ie. 15:1. A Closed Loop system works the best. I'll tell you how well this system works when I get my engine. GEOO

seano
07-11-2000, 05:09 PM
geoo,

how can you tell if you've got a "closed loop" system---is it safe to assume that because these are y2k that they are closed loop? I notice a set of fuel rails that run down the intake and have air nozzle fittin on one end and I believe the system is pressurized. I also believe that it does have an O2 sensor, but where would that be?

GEOO
07-12-2000, 05:54 AM
SeanO, Most MPI have Air Temp sensor to adjust for air density. An O2 sensor is an Oxygen sensor which mounts in the exhaust. The newest type of O2 sensors are wide band. They can measure from 9.5:1 air/fuel mixture up to 19:1 or so. The older type O2's could not measure below 14.7:1 ratio the computors had to guess on the amount of fuel to add until the mixture was over this point. The wide band type is alot quicker. I read alot about MPI's I can't wait to see how this new ECU works.
If the MPI does not have an O2 senor, then it uses a vacuum sensor & Rpm to calculate air consumption or an air flow meter, then uses a preset map to figure out the amount of fuel to add. GEOO