Definitely lean. And I see you have an ear for bench tuning which is good. I wouldn't go reinventing your engine just yet. It should at least run the way it is.
If you are absolutely sure there are no air leaks then I would say a bad bearing. A bad bearing will make the engine very eratic while running and it will cut off no matter how lean or rich you are running. Your plugs always look lean because you have to run a relatively leaner setting just to run.
When you say definitely lean, is that conclusion made from the condition of the plugs in the picture I posted? What's the best way to check my bearings? Look for play in the crank, in & out and up and down? Also I said before I start the engine with the plug loose and after one attempt the entire head around the plug is full of fuel. One thing I just thought of. I usually add a large amount of After run oil after each run. Then prior to my next run, I pull the plug and turn the engine over a few times with the starter to get the oil blown through. I was thinking maybe I'm not getting all of the oil out and it's lingering in the bottom of the case. I assumed it would definitely be blown through once the engine is running, but you know what happens when you assume. I'll pull the engine apart and check the bearings and clean all the oil out then wipe each part with oil and reassemble. Then run it and see if I have the same problem. The only problem is I'm eating plugs faster than I'm burning fuel. lol.
When the plug element is dull you ar elean. Shiny means rich. A good needle well leave the element somewhat dull.
To check you bearings, disassemble the engine. Leave the crank in. Hold a screwdriver to the case of the motor and the handle of the screwdriver against your ear. Turn the crank slowy and listen for grinding or a bump. Also feel for a bump. You may have to turn the crank back and forth and around several times. All it takes is one little bump or roughness. You may look a little stupid while doing this.
Adding at the end of each run is great. I use WD40 for ease of application and have never had a problem after months of storage. The engine should burn or blow out all the residual oil within a few seconds.
Blowing fuel out of a loose plug is standard. The engine while on the stand will not burn all the fuel. This is why it bogs and the revs up when giving throttle on the stand. When you launch the boat a load is applied and you start burning fuel.
You will get many different stories on this but the carb does not have a low end needle because most found that it restricted the high end fuel flow and that it really is not necessary. Lacking the low end needle you will need to give throttle while starting. Most people will close the carb to draw fuel and then open it to get some air while applying the starter. You kind of jog the throttle. Open - Close.
