Omc cobra 5.0 with ford 302 engine Holley carb help

Good afternoon,

first post. I haven’t run my boat in 4 years. I used resources like this forum and YouTube to replace the spark plugs, spark plug wires, change lower unit gear lube, change oil and filter, change fuel filter and drain old gas fill with new gas. Boat started, which was a surprise. Some black smoke, which is gone now.

specs say idle rpm should be 550-650rpm. Lowest I can get at idle is about 1200 rpm. Is this ok? Also, with my Holley 2bbl carb idle screws each backed out 1.5 turns, my curb idle screw needs to be pretty tight to be at that 1200rpm range.

here is a short YouTube video I made to show what happens with idle screws all the way in (I think I read that may prove something is wrong with the carb). Is something wrong with the carb? I can do more videos or photos if needed.

https://youtu.be/zobWYnOP-q8

thx

If it runs with the idle screws all the way in then it’s not running off the idle system. Turning the screws in all the way should stall the engine. The idle system may be clogged.

It's tough to tell from the video, but it does not appear to be idling at 1,200 RPM.
I would suggest that you verify that your tachometer's accuracy.


By the way...... the two screws (on either side of the metering block) are your low speed fuel metering adjustment screws.
As Louc said, when turned fully in, the engine should stall out.

The single screw is your throttle plate idle stop screw.
This adjustment governs the throttle plate position and closure.
When fully closed (screw backed out), the engine should stall out.



.

On the Holley there are idle transition slots that provide fuel as the throttle is opened, if the idle is set properly these will appear as a square below the closed throttle plate, if the ilde speed setting is set too high it will expose too much of this slot and it will start drawing from main system instead of the idle system. I think you should hook up an accurate tach to the coil and check again, and get a rebuild kit for the carb and make sure all the idle passages and air bleeds are open.