running rich
 

Changed my plugs yesterday and they are all very black. Looks it is running real fat. Engine is a '94 genV 454mag with a weber 750 4 bbl. Engine seems to run fine, but would it help to lean it out a bit. I know there are a lot of factors that go into carb adjustments. Is there a way to lean it out a little without changing the jets? The book doesn't say a whole lot about these carbs. I'm pretty ignorant about Weber carbs, so sorry for such a simple question. Thanks, Andy

Make sure your flame arrester is clean as a whistle before touching the carb.

BT

As far as I know, there is no way of leaning out a carb without replacing the jets or metering rods. How was it running before? Chances are, if it suddenly developed a rich condition, there may be a problem in the carb. Maybe dirt in the bowls.

Make sure the choke is not sticking partially closed.
Jeff

the flame arrestor is clean, and I have the choke tied wide open, so looks like I need to change the jets. But I will check for dirt in the bowls didn't think of that. thanks guys

You are only seeing the mix condition created at idle. Be careful when changing jets because you could create a lean condition at mid range or WOT that could cause serious damage to the engine. I would recommend buying Dennis Moores book on performance marine big blocks. He gives a good description of how to determine proper jetting by testing the boat.

BT :cool:

plugs
 

If you last ran the boat / idled it forever - winterizing it or even dumped some oil down it - while winterizing it, I wouldn't touch what isn't broken.

Threads here - say rich at idle is common. only good plug test is to run warm, then at speed and IMMEDIATELY shut off motor and THEN check the plugs.

Again, if it isn't broken ........ Rich cost some economy - lean can cost you a motor......

MAV

There's alot more information we need to know before I would tell you to change the jets.

One thing I do know for sure is that the choke system (Bi-metal) on that carb is always going out of adjustment. This is especially true if you adjusted it at the beginning of summer and still running it late into Fall. If you notice black smoke when you start it, then it's probably the choke.

You might have the idle mixture set too rich also. Turn both the screws in until they bottom out, then bring them both back out to about 1 1/2 turns. That should get you close.

Bob

Thanks Bob,I'll check the idle mix this weekend. Changed my mind on the jets I sure don't want to lean it out too much. Maverick, will also run it a while, then pull a plug while engine is at operating temp. Good advice, thanks guys. That's why I love OSO. Andy