View Full Version : 85 SS PCM 351W Running Rich

06-03-2009, 11:13 AM
At the end of last season my fuel pump went out, while I was waiting for the new pump I rebuilt the carb(it was a mess, I am amazed it ran as well as it did), so after I get the new pump in and the rebuilt carb it is running rich. Black smoke from the exhaust, plugs are all black, takes about half throttle to get it to start and had to adjust the idle to 1200rpm to get it to keep running.

My thought is the gummed up carb happened to be gummed up enough to keep the fuel mixture correct, and now that it is cleaned it is pushing too much fuel. This boat is originally from CA running at sea level, and I brought it to Utah running it usually around 5000', so I am thinking I should change the jets. Anyone know what size I should be running at 5000' with a PCM 351W, 4160 carb? Or any suggestions on how to find out?


06-03-2009, 04:34 PM
No idea on the jet size, sounds like you're off by a few sizes.

Have you adjusted the air/fuel mixture settings?

06-03-2009, 04:40 PM
I have tried adjusting the screws but it doesn't seem to make much of a difference.

06-03-2009, 05:05 PM
The air fuel screws should make a difference, My boat needs adujusted when the temp goes from 70 to 90. And then it starts and runs good again. Maybe you should check your points gap.

06-03-2009, 05:14 PM
I've switched to electronic ignition. The screws may be making a difference, but to me no matter how far they are in my exhaust is still black. Also besides the smoking and rough idle the boat still pulls really well.

06-03-2009, 10:58 PM
Thats odd. Ill ask My buddy who rebuilt my carb if he knows anything about it.

06-04-2009, 02:23 PM
If the boat was running fine at the altitude you are at prior to tearing apart the carb. ,I think you may have a leak or something flowing in your rebuild where it should not be. The idle mixture adjustments should make a difference and if they do not you have fuel flowing somewhere. You should check the accelerator pump or more than likely your float(s) are not set correctly. At idle if you look down into the carb you should see no fuel flowing from the venturies at the top of the carb. At idle, the gas flows at the throttle plate. I would check the floats before you start rejetting.

Good Luck.