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View Full Version : 96 Prostar 350 TBI black smoke


supturb89
07-05-2013, 12:43 PM
Last two times out I have started to notice black smoke at idle. It seems to get worse as the engine warms up. In the past the engine has always had a little white smoke at startup, but nothing like this. Motor isn't using any oil. I have also noticed a significant amount of black soot build-up above the swim platform. Motor is the standard 350 TBI. I have always thought that it has ran a little rich since I have owned it just based on the smell of the exhaust? Any help would be appreciated.

gweaver
07-05-2013, 02:18 PM
I'm not familiar with the EFI boats, but from an automobile perspective, I'd look at an O2 sensor or throttle position sensor. If one of those has gone bad (assuming the boat has them), that could cause a situation where the engine would run rich. O2 sensors are easy enough to replace on a car, it might be worth checking to find out if the boat has them.
G

mikeg205
07-05-2013, 05:29 PM
Get a code reader for michigan motorz... will most likely show a code... $59ish bucks.

Mark rsa2au
07-05-2013, 06:51 PM
Mine was doing exactly the same thing. Same motor! Check the engine temp sensor as this will tell the computer the motor is cold and run it rich. They are cheap to replace,or you can test their resistance etc. I also replaced the 2 injectors as they were filthy. I have also now had them professionally cleaned and keep them as a spare.

My money is on the temp sensor. It is the 2 wire unit out the top of the head near the throttle body sensor. Also when you replace it check inside the hole / head as mine also had a huge build up of muck arround the sensor which would not have helped either.

supturb89
07-05-2013, 08:36 PM
Thanks for all the replies guys. Will check for codes and also look at the engine temp sensor. Would this sensor cause the ECM to throw a code?

Mark rsa2au
07-05-2013, 09:18 PM
Thanks for all the replies guys. Will check for codes and also look at the engine temp sensor. Would this sensor cause the ECM to throw a code?

It did not show any codes on mine, it was just reading about 15 degrees off when I tested it.

supturb89
07-05-2013, 09:31 PM
Mark,

Can you point me to where the engine temp sensor is. Is it in the throttle body? I'm not finding a 2-wire unit in the throttle body? There is a 3-wire sensor which I believe is the TPS and a 4-wire unit that I believe is the IAC. Am I looking in the right place? Thanks.

Aaron

mikeg205
07-05-2013, 11:22 PM
should be in t-stat housing behind t-stat housing.... post a pic of the top of your engine without any covers on it.

Mark rsa2au
07-06-2013, 12:04 AM
Aaron

It is not on the throttle body / manifold but it is on the same side of the head as the TPS ie Left if you face the rear of the boat. I have a great photo but the site does not seem to be uploading photos so I will try to explain.

On the left of the motor, it is installed verticaly downward from the top of the head. It is in the area behind the water pump / under the electronic gear/ to the right of the oil filler cap and slightly ahead of it. It has 2 wires to it White and Black which end in a black clip that clips onto the sensor.

You will use a LOT of fuel if this is faulty. I was running 2 to 3 tanks a day untill I fixed the issue ( multiple issues ). My boat looked like a diesel... and yes 2 families sking hard, at least 2 tanks a day so it was a priority to find the fault :eek:

If you want to test the OHMS resistance there is a thread of mine called "temp sensor resistance" (I think) that compares the resistance of my old unit / new unit and the factory spec.

supturb89
07-06-2013, 08:37 AM
Mark,

Thanks for taking the time to write the detailed description, however I still can't find anything like what you describe in the area you describe. The only thing that comes close is a sensor below the exhaust manifold on the left side of the motor. It sits just above parallel with the spark plugs and sticks straight in. It has a black and yellow wire going to it (pic (http://i146.photobucket.com/albums/r252/supturb89/1996%20Mastercraft%20Prostar%20205/sensor2_zps9ee80c02.jpg)).

Here are some other pics of the area you are referring.

pic1 (http://i146.photobucket.com/albums/r252/supturb89/1996%20Mastercraft%20Prostar%20205/engine1_zps2f390cd6.jpg)
pic2 (http://i146.photobucket.com/albums/r252/supturb89/1996%20Mastercraft%20Prostar%20205/engine2_zps98731c36.jpg)
pretty sure this isn't it, but what is it???? (http://i146.photobucket.com/albums/r252/supturb89/1996%20Mastercraft%20Prostar%20205/sensor1_zps2c907db3.jpg)


Thanks again!

wtrskr
07-06-2013, 08:47 AM
That last picture is your knock sensor.

I'm pretty sure it is one of the two wires near the front of your engine on that first picture. I believe the one on right near the triangle (which is the t-stat) is the temp sensor for your dash. The one on the left is the temp sensor for the for the ECM. Not 100%, but think that is the case.

supturb89
07-06-2013, 08:52 AM
Thanks wtrskr,

I believe you may have them switched. The larger sensor on the left has been replaced when I was having issues with my temp gauge.

wtrskr
07-06-2013, 09:05 AM
I've always thought mine might run a little rich so I may test mine too. Let me know how you end up going about testing if you do. Mine throws no codes but I do get a little soot buildup just below and around the exhaust flaps.

If you want to test for codes, you don't need to buy a scanner. You just need a paper clip.

Does your dash have an engine temp light for warning of an overheat? If so, you turn the key to the ON position, engine OFF, then put the ends of the paperclip into terminals A and B of the code scanner thingy. It will start flashing the codes on your dash light. You can google paperclip and code reading.

supturb89
07-06-2013, 07:20 PM
Mark,

Thanks for the info on the engine coolant sensor. Changed it out today and the boat great with no black smoke. I didn't even have to wipe around the swim platform after pulling it out of the water!

wtrskr,

Before installing the sensor I tried the paperclip trick but my check engine light didn't flash anything at all, not even the code 12? I'm guessing that the light is not even hooked up for some reason. I have a "check engine" and "transmission temp" light on my dash. Are these supposed to light up at any time during start-up like in a car?

Thanks again gentlemen.

Aaron

wtrskr
07-06-2013, 08:42 PM
Mark,

Thanks for the info on the engine coolant sensor. Changed it out today and the boat great with no black smoke. I didn't even have to wipe around the swim platform after pulling it out of the water!

wtrskr,

Before installing the sensor I tried the paperclip trick but my check engine light didn't flash anything at all, not even the code 12? I'm guessing that the light is not even hooked up for some reason. I have a "check engine" and "transmission temp" light on my dash. Are these supposed to light up at any time during start-up like in a car?

Thanks again gentlemen.

Aaron

Glad you got it fixed. Did you have the ignition key turned to the right when you tried it?

On my '94 I don't have a check engine light but there is another method to see the flashing. You take an led light (small trailer light or something like that) and you put the ends into, I want to say, terminals E and F. Those give the power for the led light. You don't want to screw up the terminals so I'd double check that somehow first. It can be a little tricky holding the paper clip and the led light at the same time.

Mark rsa2au
07-07-2013, 05:25 PM
My temp sensor did not trigger a code! Follow the paper clip method but don't be surprised if there are no codes.

chrislandy
07-08-2013, 09:36 AM
Mark,
Before installing the sensor I tried the paperclip trick but my check engine light didn't flash anything at all, not even the code 12? I'm guessing that the light is not even hooked up for some reason. I have a "check engine" and "transmission temp" light on my dash. Are these supposed to light up at any time during start-up like in a car?


I had this problem last month, the check engine light should come one when you turn the ignition on, just like your car, then go off when started.

Mine never came on as in never for the last 10/12 yrs I've had it, it turns out it was never connected!

There was a stray wire (brown-purple I think) in at the rear of the engine not connected to anything. Plus there is a white 2 pin connector floating around in the same region which on mine had both bungs in the socket side i.e. blanking it off. I compared it to a 97 ProStar with the same engine and that spare wire was connected to the plug. I did a few checks with a multi-meter and a test light then plugged the wire into the matching pin and like magic the check light works :) - finally got some fault codes out of it :)

Chris

supturb89
07-10-2013, 10:31 PM
I had this problem last month, the check engine light should come one when you turn the ignition on, just like your car, then go off when started.

Mine never came on as in never for the last 10/12 yrs I've had it, it turns out it was never connected!

There was a stray wire (brown-purple I think) in at the rear of the engine not connected to anything. Plus there is a white 2 pin connector floating around in the same region which on mine had both bungs in the socket side i.e. blanking it off. I compared it to a 97 ProStar with the same engine and that spare wire was connected to the plug. I did a few checks with a multi-meter and a test light then plugged the wire into the matching pin and like magic the check light works :) - finally got some fault codes out of it :)

Chris

Thanks for the info. Will look around more next weekend.