Poor running 3.0 Mercruiser

[Willy.Fire]

Thought I would start a new thread about just the engine. So I took it to the lake this morning here is what happened.
Started great with 3-4 pumps of throttle turn key over then pump throttle 3-4 more times and it fired right up. Let it warm up just above idle for about 4 minutes everything seemed great. Push off engage reverse and works great. Back to neutral and as soon as I engage forward it stalls. So I get it fired back up only way is to full throttle while cranking but as soon as I throttle back it dies trying this 3 - 4 times. To get it going I had to quickly go back to neutral and put it into full throttle instantly. So ran for about 4-5 minutes good but not letting the rpms go down then when I did decide to turn dropped rpms ran ok but then when I went to go full throttle again it just limped along at about 60-75% so I took it back to the dock.
Thats not it...Got it out of the water pull drain and a little oil comes out ): look in engine bay and theres about 500ml of oil. So now I have a oil leak. When I idled it in the driveway for about 25mins yesterday I was watching engine and did not notice anything leaking. I took a few pics I found what looks like a screw missing on the top under the yellow hose coming from the carb. But no idea if this is where its from. I did have the engine spotless from cleaning yesterday. Thanks for any advice before its off to the mechanic.

[mmwjr]

Not sure I can tell where you are seeing the missing screw but it looks like some oil onto of the manifold runner by the yellow site tube.

Sounds like two separate issues. The not wanting to idle can be several things; water in fuel, choke not opening, vacuum leak at base of carb, or carb issues.

[Willy.Fire]

sorry thought i added pic with missing screw/bolt circled. the oil is all along the top area there and looks like dripped down from the top so Im hoping nothing to serious. should I run it again and wait longer see if I can find any leak only if I wont hurt things more?

[mmwjr]

I can actually see it better in picture two of your first post but cannot tell for certain but it looks like a valve cover bolt is missing. This would explain the oil leak which will only occur when running the engine.

Is any oil getting into the carb? May be choking it which keeps it from idling.

[Willy.Fire]

I really know very little about carbs other then how to start a engine with them so not sure about the oil? I would love to learn but also dont want to try things Id be better off paying for. How could I tell? Im taking the boat to a friends mechanic tomorrow who is very good he used to work and own the local yamaha/mercury shop but I hate paying for things I may be able to fix on my own. He is rebuilding carbs and replacing water pump impeller and now this oil leak unless I can fix it. Should I run in my driveway to see if oil comes from that area or does it need to be higher rpms? Im guessing around the gasket below?

[mmwjr]

You can try running it but higher rpm may be required. If it is the source of the leak I would replace the gasket for the valve cover.

You can remove the flame arrester to see if any oil is inside and on the carb ventri