Yes i look at those manuals and think my motor doesnt even look like that.
To answer your questions id just put your throttle to full (with engne off) and check your butterflys a flat.
Now as you lay back the throttle they will close. Whether it hits on the precise point it should or not i wouldnt worry much at this stage. You can sort that out a bit later or i can take a photo of where mine is at to give you an estimate. Its winter here in New Zealand so my boats under cover.
And now for idle timing screw. You cant just back that in to make it look good like mine. You have to do that in a barrel or in a lake when the motor is warm, and back it up until the motor doesnt quite stall and i mean doesnt quite, it will almost sound like its stalled but it will keep going. That is a perfect idle setting when you get to that. I did mine once and ive never adjusted it again.
Now for the crucial part. You cant just back that screw in and reduce your rpm so the screw is like mine. You see with lower rpm the engine has to have everything else going well to make it be able to keep alive. SO in one sense you can say that the lower you can get the motors rpm without it stalling the more healthy your motor is.
Mine does not have great compression, it is probably less compression that yours so if everything else in your motor is right such as the carbs/ crankcase seal you should be able to get that screw in as far as mine or more, my thoughts are you wont be able to as there seems to be some kind of slight miss indicating a problem so you will have to keep a higher idle speed and therefore work out whats wrong.
But go give it a go and see what you can achieve
