Black "soot"'on transom

[Shabah180]

Hey guys, ive only put about 3 hrs this season on the shabah 180, first time the 350 mag ran flawlessly, and still does. I pull it put of the water when were done the weekend at the lake, and the last time i noticed a black soot around the transom. When i splashed it, i was standing and when i sat down, my leg must have hit the run/off switch to off and i believe i flooded it.
Would this had caused the black soot? Is it normal for a motor to idle perfectly and still have the fuel/air mixture in the carb out enough to run rich?
Another thing is i filled it with premium gasoline with no ethenol.
Its a bugger to clean, its just wierd that all of a sudden it can run one weekend with no soot, then suddenly it can appear! Haha!
I guess i can haul it into a merc tech, but if i dont have to it means more time on the water!
Thanks guys.
Cory

 

[alldodge]

That stuff is caused by the motor running a bit rich. I forget but think yours is a carb

 

[Shabah180]

That stuff is caused by the motor running a bit rich. I forget but think yours is a carb

Yes 4 barrel pre vortech. Next weekend ill see if it does it again, its hard to get it off the gelcoat. Lol
Still idles good, seemed to sputter once during the hole shot, was a little scary cause it hesitated, and right in the middle of me muttering "'what the hell.." It shot out like rocket haha!
I watched some videos on how to adjust carb fuel air mixture on a merc but didnt see if its the same on a 2 barrel as opposed to a 4 barrel.

 

[stonyloam]

With an electric choke it will run pretty rich until the choke opens, I know mine will put out some black smoke for the 45 seconds or so, and I can get a little "black soot" on my transom. Once you get it cleaned off you might watch on startup to see if that is where it is coming from.

 

[Shabah180]

With an electric choke it will run pretty rich until the choke opens, I know mine will put out some black smoke for the 45 seconds or so, and I can get a little "black soot" on my transom. Once you get it cleaned off you might watch on startup to see if that is where it is coming from.

Thanks terry, mines a '95. Mercruiser 5.7 4 barrel not sure if it has an electric choke, i normally have to pump the gas a few times and it fires right up. I guess pumping the gas into the carb would be the same as choking it?

 

[thumpar]

Pumping the gas will also "set" the choke. My old boat would do the same thing.

 

[Shabah180]

Pumping the gas will also "set" the choke. My old boat would do the same thing.

Ok so this is a fairly common occurrence. I dont see it happening when your up to speed and moving, for it to cover the transom like that along the waterline it has to be happening at idle.
Just another rookie freakin out! Haha!

 

[thumpar]

Once the choke opens it shouldn't happen at any speed. You can check to make sure your choke is opening fully.

 

[Shabah180]

Ok thanks again.

 

[HT32BSX115]

Is it normal for a motor to idle perfectly and still have the fuel/air mixture in the carb out enough to run rich?
Another thing is i filled it with premium gasoline with no ethenol.
...............
Thanks guys.
Cory

Hi Cory,

It doesn't matter what kind of gasoline you use.......

It's very likely that your automatic choke is either adjusted wrong or it's "sticking" closed until the heating element gets completely hot........

Then medium to high throttle settings finally force it open.

I have never liked automatic chokes on boats since they're a sort of one-size fits all. You run REALLY rich until the (bi-metallic) element gets hot enough to hold the choke open.

If you boat in fairly cold weather this is probably good since you need a fairly rich mixture during start-up and initial warm-up.

If you don't boat in cold weather, you can almost adjust the choke right "out of the picture" or wire it open and disconnect the electrical connection

I only operate my boat (carbureted 454 Bravo) in warm weather. I installed the engine in 2006 and never did connect the automatic choke, and I adjusted it so that it can never activate.

Other than having to pour a small amount of gasoline in the carburetor after parking the boat from AUG---JUN, to get it to initially start (because the carb is likely dry), subsequent starts only need a couple of "pumps" of the throttle to prime and start. Then I run at a slightly higher RPM (using the throttle) for a warm up before boating.

Once the engine is warmed up, it's good for the rest of the day and only needs maybe 1 "pump" of the throttle to start.

If you like to boat in cold weather, you're probably going to need the choke to operate. I have operated my boat in weather that was cold enough that I didn't want to go in the water but I have never had any problem getting it to start.

Below is a Youtube video (#1 of 4) that describes how an automatic choke operates.

https://www.youtube.com/watch?v=MzCEcrj6aMM


ymmv,

Rick

 

[Shabah180]

Hi Cory,

It doesn't matter what kind of gasoline you use.......

It's very likely that your automatic choke is either adjusted wrong or it's "sticking" closed until the heating element gets completely hot........

Then medium to high throttle settings finally force it open.

I have never liked automatic chokes on boats since they're a sort of one-size fits all. You run REALLY rich until the (bi-metallic) element gets hot enough to hold the choke open.

If you boat in fairly cold weather this is probably good since you need a fairly rich mixture during start-up and initial warm-up.

If you don't boat in cold weather, you can almost adjust the choke right "out of the picture" or wire it open and disconnect the electrical connection

I only operate my boat (carbureted 454 Bravo) in warm weather. I installed the engine in 2006 and never did connect the automatic choke, and I adjusted it so that it can never activate.

Other than having to pour a small amount of gasoline in the carburetor after parking the boat from AUG---JUN, to get it to initially start (because the carb is likely dry), subsequent starts only need a couple of "pumps" of the throttle to prime and start. Then I run at a slightly higher RPM (using the throttle) for a warm up before boating.

Once the engine is warmed up, it's good for the rest of the day and only needs maybe 1 "pump" of the throttle to start.

If you like to boat in cold weather, you're probably going to need the choke to operate. I have operated my boat in weather that was cold enough that I didn't want to go in the water but I have never had any problem getting it to start.

Below is a Youtube video (#1 of 4) that describes how an automatic choke operates.

https://www.youtube.com/watch?v=MzCEcrj6aMM


ymmv,

Rick

Awsome! Thanks for taking the time to explain that! At nights here it can get cooler ( 12-15 celcius) in the spring and fall, not sure if that classifies as colder weather, needs to be pretty cold for a canadian to say that... Lmao!
I will definitly check if the choke is sticking before i splash it, the first 2 times she ran without the black residue, only the 3rd time i had her out for a burn i noticed it.
So i need to pull the flame arrestor off and expose the carb?

Thanks again gentlemen, you guys know your stuff.

 

[Shabah180]

That was a good video. Im going to keep it on hand when i go to the lake and expose the choke and see if its operating correctly and at the right adjustment, i can see now why it was sputtering at cooler engine temps on throttle, normally i wait until its at operating temp before i leave the dock!!