1990 454 Crusader releasing black soot and gas slick from the exhaust

Hello again just when it seems that I have the engines under control something else rears its ugly head. This past weekend I noticed 4 things different on the port engine - 1. black soot coming out of the exhaust and leaving a slick on idle, 2. a gas slick the same and 3. the gas smell appears to be greater than before. I have 4 barrel carburators that were rebuilt not long ago and i replaced the filters in line and on the carburator this year. One other thing the port engine will not generate rpm above 2800. These 454's I was told are great engines but i have yet to experience anything but great Its getting to the point where i am afraid to leave the dock

Any ideas or suggestions other than using the engines as anchors?

Have you pulled a few plugs to see if they are all sooted up ? Maybe then followed by a compression check?

No sir I have not pulled a plug yet but that is a good idea - i did change the plugs10 hrs ago so never thought to pull them. This is an engine that I cooked ( 230 degrees ) a few months ago by way of the fan belt blowing off under way. At the time no water was in the oil and since that time I thoroghly cleaned the u cooler, risers and elbows, changed the impeller and oil and filter. The engine seems to sound ok but the smell of fuel has increased.

Not sure if any of this info helps you but I am all ears.

Thanks

You may have a cracked head, not good news, I know, but 454's just don't take heat well. If you got hot enough to blacken anything, you may very well need a head. You can try a compression test, but does not always rule out a crack, depending on where it is.
Good luck !

When you hear hooves, don't think zebras. I would rule out the carburetor before doing anything else. Look down the throat at idle, does any gas drip (or spray)out of the primaries? I'll bet yes. Once you rule out the carb, then move on to the more expensive issues.

One of mine did that when I, ah, installed the, ah, impeller backasswards and overheated it a bit. It DID go away, though. Is the motor now running the correct temperature?


Jeff

When the carbs were rebuilt, did they just use the "standard kit"?

if so, I'd bet the float should have been replaced.

Another item to check is the "sight tube". if it is full, it means install a new fuel pump. The sight tube will "dump" any fuel provided to it into the primary bore, right above the fuel inlet (starboard bore on an in-line install).

Don't worry, I'm sure the plugs have sooted up....no way for them not to with that much fuel flowing into the engine.

All good points - will proceed - if the head is cracked what other symptoms would be occurring? It seems that the issue is fuel related with the gas and soot slick isnt it?

Thanks for the feedback great site has been very helpful.

The engine is normal is temperature - I shot an infrared heat gun all over the block, exhaust and water cooling systems and all temperatures were normal.

Not sure on your questions re the carb rebuild - it was done before i bought the boat

Then check the sight tube and check the primaries like sammi suggested. If you see liquid, pay attention to its point(s) of origin. Also, note the condition of the airhorn gasket, around its perimieter. if it is damp/wet/dripping, its a confirmation of a flooding condition.