My 5.0 runs great through the midrange and up top, but at idle it will slowly lose rpm, run rough and eventually stall. If I give it some throttle, it perks back up and will continue to run. Once back at idle, it does the same... It starting this last season, but seems to be worse now. I have changed plugs, cap, rotor, rebuilt carb last season( 8 months )I am planning on another carb clean, but any suggestions would be great.
I had the same issues. I ended up buying a rebuilt carb from Guaranteed Carbs around $300 exchange. It runs perfect now, I only had to adjust the choke. There are some tiny ball valves I could not get out to clean and do not come in a repair kit.
I have changed the filter, and I am going to have the carb rebuilt soon. I ran it today, and when I look down through the top of the carb at idle, I have fuel dripping into both chambers, that is normal... right?
Dripping fuel is not normal.
Sounds like your idle issue is related to an over rich condition as a result of the dripping.
This can happen if the float level is to high or needle/seat are dirty. Another possibility
is the float is saturated or if a brass float, it has a pinhole and is filling with fuel and not rising to the point of closing the needle fully.
I had this same issue and found it was a combination of a bad float coupled with a dirty needle. I rebuilt both carbs with kits from Mikes Carburetor and problem solved.
You will have a choice of a solid shaft needle or a spring loaded one. There was a bulletin on this and the float adjustment is different for each.
I removed the carb, cleaned again, and actually adjusted the float to 22mm from 18... fuel still drips at idle. The boat runs excellent at WOT, but blubbers and eventually dies at idle, I would agree on the rich condition. Last season I replaced a bunch of things at once, one being the fuel pump. I replaced the stock mercruiser with a low pressure fuel pump from " the fuel pump factory" I am now wondering if it is putting out too much fuel, floating the float and dripping into the Venturi..... I haven't checked the fuel pressure due to the rigid line... that being a giant PITA. Do you think those pumps are junk?
I’m confused. The float drop sets the full open, and float level sets the shutoff point.
Float level Specs call for 9 to 14mm depending on the application and the type of needle (spring loaded or solid). This insures that the needle shuts off fuel when the bowl fills.
If the level is too low, needle never seals off the incoming fuel and you get dribbles.
No opinion on the pump yet, as it seems you still have carb issues
So.. here I am again. I have just had the carb professionally gone through, I put in a new Mercruiser fuel pump....I am still having dripping into the Venturi. Like I have said in the past posts, the boat runs excellent up top, when at idle it slowly drops rpms, and then dies, from what I believe to be a too rich mixture with the fuel dripping at idle. I am totally stumped. I haven't checked fuel pressure, but I am having a hard time believing that a new mercruiser fuel pump is giving me the problems. it is a low pressure pump. Any advise would be appreciated.
Your theory on over rich is valid. Checking fuel pressure to be sure it’s in the 4-5 lbs range would would eliminate one potential issue. I still think you have an issue with the fuel level.
Verify from the rebuilder that he checked the float for saturation/pinholes. Verify the float settings (see my prior post). Float level too high = dribbles. Last item may be the check ball (link below). https://www.carburetor-blog.com/know...-from-venturi/
Also, What does your rebuilder have to say about the issue?
5.0 runs rough and stalls at low idle
Linear Mode
