Grr. Black smoke from the exhaust

A

Angrywasp

Petty Officer 2nd Class
Joined
Mar 1, 2010
Messages
101
Well after my third attempt to take the boat out and having it die (again) after starting to drive it to the dock from the trailer I took the boat home. It had fouled the plugs again (same thing it did the last 2 times). I leaned the carb out a half turn and had it running on the muffs in the drive for about 10 mins so it was up to temp (right in the middle of the green band) and running fine. Then it started sending black smoke out the exhaust so I immediately shut it down. I had some issues with compression a couple of weeks ago but got the boat running and it didn't seem to affect the way the motor ran once I replaced the ignition module. I was leaning towards the headgasket (and am again) when the ignition module issue popped up since I had low compression on 2 cylinders. I'll have to investigate more tomorrow but I'm open to suggestions right now. Any ideas? I'm beginning to think my boat is afraid of the water.
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Grr. Black smoke from the exhaust

Is the choke open when the engine is warm? It better be.
 
7

79Glastron

Petty Officer 1st Class
Joined
Jul 18, 2007
Messages
256
Re: Grr. Black smoke from the exhaust

Black smoke is rich fuel mixture. I doubt your idle mix screws will cause your problem. I would be looking at sticking float, damaged needle and seat, and of course, stuck choke. Do you have clean fuel? Whats your fuel filter look like? Might be time to rebuild the carb. I could see a very, very dirty flame arrestor causing you to run rich also, but unlikely. A look down the carb throat when its acting up will tell the story.
 
A

Angrywasp

Petty Officer 2nd Class
Joined
Mar 1, 2010
Messages
101
Re: Grr. Black smoke from the exhaust

I'll check both tomorrow. The boat will rev fine (out of gear) in the water. It just shuts down when the motor has a load on it.
 
6

6meter

Chief Petty Officer
Joined
May 15, 2010
Messages
525
Re: Grr. Black smoke from the exhaust

You mentioned compression issues. They don't come and go. How low is the compression? You are running very rich. Might be fuel in the oil, washing the cyl walls or blow by vapor going in the carb through the vent hose. Along with what others have mentioned.
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Grr. Black smoke from the exhaust

Have you pulled the dip stick and done a sniff test for presense of fuel? Is the oil level over full? Both signs that you have a serious carb problem. Such as needle and seat not sealing. Lots of black smoke says "waaaaayyyy" rich. With a warm engine the choke plate should be standing verically in the carb bore. If not, start there.
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,082
Re: Grr. Black smoke from the exhaust

Ayuh,... I agree, at 1st glance, the Carb is probably Boogered up, Big Time....
But,...
A ruptured mechanical fuelpump diaphram could also be the culprit...

Does the semi-clear tube between the fuelpump, 'n carb have any fluid in it,..??
 
A

Angrywasp

Petty Officer 2nd Class
Joined
Mar 1, 2010
Messages
101
Re: Grr. Black smoke from the exhaust

Okay. Here's what I've found so far. The carb settings were way off so I checked everything against the manual and set it all to factory spec. It started right up after with no problems and no smoke. I let it warm up good and started dialing in the idle. I noticed a change in the engine tone and checked the gages. The temp gauge was almost to the top of the green band so I shut it down. Well I pulled the impeller housing off and it was completely dry (and impeller toasted). Turns out my muffs are bad (could squeeze them with the water on and impeller out and water would come out the housing but wouldn't if I wasn't squeezing them). After about half an hour I decided to do a compression test and cylinders 1,2,3 were 160-175 psi while 4 was 90. The previous compression test was with the motor cold and I got 100, 50, 110, and 90. No smell of gas in the oil (although there was some water on the inside of the valve cover.) and there isn't any gas flowing through the bellows rupture hose from the fuel pump. The oil is milky looking and for some reason my oil pressure seems to be fluctuating. Sigh. Any ideas besides sinking it in the ocean while it's on fire?
 
choochooharley

choochooharley

Petty Officer 2nd Class
Joined
Aug 27, 2008
Messages
172
Re: Grr. Black smoke from the exhaust

Well it sounds like you have bad compression in #4 and with the mily oil that means water is in the oil could be a bad head gasket causing the low compression and the water....as far as the black smoke that is probably a seperate issue with the carb....my suspisons are float needs adjusting or you need to rebuild it or a stuck float.....
 
Fireman431

Fireman431

Rear Admiral
Joined
Sep 17, 2007
Messages
4,292
Re: Grr. Black smoke from the exhaust

You're biggest issue appears to be a head gasket. The milky oil is your primary concern. That would also account for your compression numbers being way off and the temp going up. They can be different, but really shouldn't vary more than 5-10%.

Once you fix that, take another look at the carb and either get it fixed correctly or replaced.
 
G

GLENN M

Petty Officer 1st Class
Joined
Aug 14, 2010
Messages
204
Re: Grr. Black smoke from the exhaust

if muffs arnt working howd you get water in engine? your cyl pressure numbers are all over to one test to low the next,what kind of tester the one you hold or one you screw in? black smoke is to much fuel.air flowing throw venturies causes pressure drop which draws in fuel,so no air no fuel
 
A

Angrywasp

Petty Officer 2nd Class
Joined
Mar 1, 2010
Messages
101
Re: Grr. Black smoke from the exhaust

My gages monitor oil temp and pressure. I don't have one for water temp. It was sheer inattentiveness on my part to not notice there wasn't water coming out of the prop in addition to what was spraying out from my muffs. I use a screw in style compression tester and compression of a motor changes depending on it's temperature. Plus if the head gasket is bad it would change also. The black smoke issue is solved (even though the plugs are still pretty black) but fine tuning will have to wait on the impeller, probably the head gasket, and a trip on the water.
 
D

dubs283

Vice Admiral
Joined
Jul 27, 2005
Messages
5,332
Re: Grr. Black smoke from the exhaust

Angrywasp said:
My gages monitor oil temp and pressure. I don't have one for water temp.
Click to expand...


huh??

are you sure the temp guage is for oil temp??

it is probably water temp unless you or somebody else changed it at some point

i can't see any engine manufacturer installing an oil temp guage and no water temp guage
 
A

Angrywasp

Petty Officer 2nd Class
Joined
Mar 1, 2010
Messages
101
Re: Grr. Black smoke from the exhaust

dubs283 said:
huh??

are you sure the temp guage is for oil temp??

it is probably water temp unless you or somebody else changed it at some point

i can't see any engine manufacturer installing an oil temp guage and no water temp guage
Click to expand...

Yeah you're right. The symbol on the gage is almost exactly the same as the oil symbol for cars. Slowly learning to pay closer attention to everything.
 
JetBote

JetBote

Seaman
Joined
Jul 15, 2010
Messages
69
Re: Grr. Black smoke from the exhaust

Your plugs will not clean themselves. They will remain black.
 
A

Angrywasp

Petty Officer 2nd Class
Joined
Mar 1, 2010
Messages
101
Re: Grr. Black smoke from the exhaust

JetBote said:
Your plugs will not clean themselves. They will remain black.
Click to expand...

Actually if you have the engine up to temperature, correct air/fuel mixture (which I still don't but it's better than it was), and the plugs aren't fouled to the point where they won't fire (which they were) they will clean themselves becuase they will burn the carbon deposits off. A butane torch and a pair of pliers will net you the same result. I've also used a toothbrush and gasoline to remove some build up too.
 
JetBote

JetBote

Seaman
Joined
Jul 15, 2010
Messages
69
Re: Grr. Black smoke from the exhaust

If you want to get a correct plug reading, you cannot use old plugs. Sure, you can clean them to get a spark, but that's the only benefit. A correct engine temp and mixture will NOT clean plugs. The carbon build up can continue to build up and prematurely detonate the fuel mixture.
 
C

ChampionShip

Petty Officer 1st Class
Joined
Mar 18, 2010
Messages
202
Re: Grr. Black smoke from the exhaust

Angrywasp said:
I'll check both tomorrow. The boat will rev fine (out of gear) in the water. It just shuts down when the motor has a load on it.
Click to expand...

Time for a complete carb rebuild- start there to eliminate variables. Alot of boats will run great on the muffs and then fall on their faces with a little backpressure being in the water......let's just say I have a newly rebuilt carb:rolleyes:
 
A

Angrywasp

Petty Officer 2nd Class
Joined
Mar 1, 2010
Messages
101
Re: Grr. Black smoke from the exhaust

JetBote said:
If you want to get a correct plug reading, you cannot use old plugs. Sure, you can clean them to get a spark, but that's the only benefit. A correct engine temp and mixture will NOT clean plugs. The carbon build up can continue to build up and prematurely detonate the fuel mixture.
Click to expand...

Seems NGK thinks otherwise. Appreciate the help though.
http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp
Just because I'm new to boats doesn't mean I don't know what I'm talking about.
I'll probably be pulling the carb this week then while waiting on other parts.
 
JetBote

JetBote

Seaman
Joined
Jul 15, 2010
Messages
69
Re: Grr. Black smoke from the exhaust

Oh, the guy that doesn't know what black exhaust means, nor knows the difference between an oil and engine temp gauge is versed in spark plugs? Ok.
 
You must log in or register to reply here.
Top