The carbs on my 2001 HP500's are running very rich at idle- black soot and smokingand more difficult to start after they have been run any length of time. Can someone clue me in on how to adjust or other. I''ve been told different things- jet down 2 sizes (doesn't seem logical for idle), turn the adjusting screws on the side in, turn the adjusting screws out. They are about 1 turn out from fiull in right now and I was told they should be out about 2/12 turms. Any tips are appreciated.

Have these been on the boat for a while and did they at one time idle and start good? If so I would put in new power valves. Jets don't get bigger all of a sudden and shouldn't affect the idle circuit.

Power valves, air bleeds, or mixture screws. They usually do end up between 1.5-2 turns out.

If you have been using ethanol fuel for a few years it would be best to rebuild the carbs, and check the floats at the same time. Ethanol will attack the internal gaskets and power valves best to refresh them. IMO

I have the same problem...rebuilding my carb this week to see if it takes care of it. When i adjusted the mixture screws it had no effect.

That will happen when the power valve ruptures, Make sure you get ALL ports and passages cleaned out and blown out with compressed air, the smallest piece of debris in the wrong place will cause headaches afterwards. let us know how it works out for you!

if you have a real black transm you may have the floats adjusted too high..or a bad needle and seat or even a piece of chit in it,,also like mentioned the air bleedes may need to be clean,,remove flame arrestors and hose the carbs bown with carb cleaner and blow with compressed air wigh a towel over the carb to keep chit from going everywere..
.2.5 turns out is way too much,,i would go 1/2 turn and see if it loads up..

Make sure your chokes are not staying closed.

Blow out the idle air bleeds using carb clean and the little red straw. Insert straw in idle bleed, blow them out. On HP500's where the valve cover breather tubes are connected to the flame arrestor, its common for them to get plugged up with oily goo residue.

Good idea to blow all the air bleeds out. They are on top of carb, when looking down into the barrels. You'll see 4 in front, 4 in back. The larger ones are idle bleeds, smaller ones are high speed bleeds.

By the way, its not jetting. So whoever told you that, steer clear. Carbs don't change adjustment on their own. If they ran fine, and all of a sudden don't, find out why before turning screws to compensate. Usually its dirt, leaking gaskets, powervalve blown, etc etc.

I just got the boat in July and don't know how it ran before as the previous owner had passed away. Even though I use non ethanol I'll bet that ethanol was all that was used. I'll take all your suggestions, and anymore that come in, and start with cleaning and go from there up to powervalves and rebuilding. Does anyone know what model # these Holleys are so I can get the right rebuild kit?