I am using the QFT M-800 carbs with mechanical secondary's. I was getting ready to put the boat in the water so I fired them up at home first and they weren't idling very well and noticed the AFR was low and mid 14's and rapping the throttle there was not a smooth transition, Not hesitation just not smooth. Anyway, I checked the idle screws and all 4 corners were only out about a 1/2 turn. I ran them out to a full turn and it seemed to be the best idle but now when I hit the water, they are running very rich. 10.9 or so and you can smell it especially when the engines were still cold. BTW, overall they run very well at this setting and the transition from idle is very good. I'm going to try 3/4 of a turn out and see what the AFR is. I assume it would be better. I have looked around and most people say 1-1/4 - 1-1/2 turns out is normal. I don't know if this is a tell tale sign that my carbs are too big for my engines? At the time, they cost the same as the 750 and bigger is better......right? Cruising the AFR is upper 12's. 454's@ 500hp. Thanks for your help.

I personally don't care what the AFR gauge reads at idle....give the motor what it wants and likes WARMED up at idle. That's why EFI became a thing because you can make on the fly adjustments cold versus hot. Likely you will end up rich when cold and just right when warmed up. You can't go off of what one person says is right as all carbs and engines are different. Usually I will set timing to desired value, adjust idle screws till the engine runs best, recheck timing, and run it. Not saying this is the scientific way of doing it but I have an ear for what a happy motor sounds like and I've been doing it for years....I know there's a way to do it with a vacuum gauge but I've never done it...try google searching idle adjustment with vacuum gauge and I think it will get you in the ballpark.

Side note...wouldn't worry too much about prop tuning until you get the motors running right either....will end up wasting a lot of time and money...just my opinion...

Your carbs are not to big.
You have to set the idle with the engines fully warmed up. Best away is with a diagnostic tachometer. Turn them out until you get the highest idle. Then adjust the idle speed stop back to your desired rpm. Repeat the procedure because as rpm increases it's easy to go too far. Most of the carb companies say 1-1/2 turns out but I've never found that to be even close. Your next issue is how they transition. Your accelerator pumps are probably not properly adjusted. Easiest way to get them right is when the throttles are closed you should be able to barely move the accelerator arm and see fuel come out the nozzles.
Good luck getting it set up right. It's well worth the learning curve.

Another tidbit I would add with the accelerator pump...make sure the arm is not too tight on the pump...I have seen the vibration from the engine cause the pump to start squirting and cause a super rich idle...I personally like to leave a couple thousandths gap between the spring bolt and the pump arm...just food for thought.

I was running on the hose and they were warmed up just to the point that they would idle so maybe not warm enough? I adjusted both of the front screws then adjusted the idle back down. I should adjust the idle after every screw instead of in pairs? The accelerator pump was adjusted by dyno dude. It had a hesitation on the dyno and he made an adjustment so that didn't happen. I'm pretty happy with the performance overall it's just too rich at idle. Maybe the accelerator pumps are a little too tight and they are vibrating and contributing to the idle mixture? I can back them off a little. Would you mess with the secondary accelerator pump too? Thanks for your help.

So I took the boat out Monday to Lake Michigan and back. Before I took off I turned all of the screws a 1/2 turn out. I had set them at a full turn and the transom had a lot of soot. I believe the AFR was mid to high 10's. When I returned this time, there was very little if any soot. Hard to tell from a "Scum Line" sometimes. Anyway, it was plenty warmed up when I returned so when I put it on the lift I thought I would mess with the carbs a little and see if I could get the AFR at least at idle corrected. I have the idle set at 800 rpm out of gear and the 4 corners are all out 1/2 turn. AFR is 11.5 ish. I can turn any screw all the way in ( I only did one at a time then turned it back out the 1/2 turn then moved on to the next hoping there would be a difference in idle quality) and the idle never misses a beat. Shouldn't it stall or run like sh!t?? I've done this before in my cars as a kid and that was the outcome then. When I installed the throttle cable I made sure it didn't pull the carb open so wherever dyno dude had it is where I had it. I also had tightened up the spring for the accelerator pump in case it was drizzling and then adjusted to a point where the hesitation went away. Not sure of the clearance but the pump was not a factor during my adjustment of the air screws because it was pretty loose. FYI, both engines seem to run fine. They don't stall out now, they did after a few moments at one full turn out, and there are no hesitations. Very smooth running from idle to WOT. Any thoughts on what I should be looking for??? Thanks for your help.

Have you put a timing light on to verify base timing is right? If not do that before anything else.
You move each idle screw together. If you got two idle screws then both in/out the same each adjustment. If you've 4 corner idle then do all 4 together. Start by lightly bottoming them all out and opening them 1 turn. Then , using 1/8 turns, make an adjustment in/out and watch the tach or vacuum gage. Tach or vacuum increases you've went the right way. Continue until you get highest tach or vac reading. Once you get to roughly 900rpm you need to drop the idle back because at that point your getting near where the main circuit starts to work. If at all possible you should do your adjustments in gear either at a dock or while someone else drives. If there's a major difference between in gear and neutral then we need to get into a different aspect of tuning. But this is the best way to start out.

From Smitty275 "Have you put a timing light on to verify base timing is right? If not do that before anything else." My question is, What is a good base timing for my engines? Also if I am looking for a total advance of 33 degrees and the base timing is off, I adjust for base then total is off. I know that in my "ready to run" marine MSD distributor he removed a part and installed the black one. Had something to do with total advance? I don't have the other "colors or parts" so not sure I can easily change stuff if necessary. Also this is just FYI, the boat starts easily, transitions well from idle through the primaries and then into the secondary's. I'm going out today with my "Pedestrian data logger" (GoPro for short) and try and post some info. Thanks again for your time.

The black bushing allows 14° of advance. So your base timing is going to be 20° to start with. I'd set it at 800rpm because we don't know what springs are in it.

The springs are a combination of the light and medium. Thanks for your help.