The manual for other engines uses 675 RPM in F gear idling, boat moving in the water...fast enough to keep the engine running, slow enough to keep from klunking when shifting. I don't have, nor have I ever been around your particular engine but it shares similarities with other specimens of the species.
You must have a Quicksilver Commander 3000 control where you push the big button and advance the lever toward the dashboard and you have throttle with no gear shifting. When starting the engine, especially cold first start, I always disengage and move the throttle up to probably 45* toward the dash. It's like back in the old days before cumputer controlled ignition systems: You press the accelerator pedal all the way down to set the automatic choke mechanism. You let off the pedal push back down about half way, roll the key to start and when it lights off you let off the pedal and maybe bump it a couple of times till the engine stabilizes. Then after somewhat warm, you rev it up instantaneously to get the automatic choke linkage to release and let off the gas with the car idling smoothly at idle RPM.
When you have disengaged the shift function as I mentioned above, and advance the lever, you are not in Forward Gear. Your gearbox is in Neutral until you pull the lever to the upright position whereby the button pops out and the lever again becomes shifter and throttle.
What you haven't touched upon is your choke or "fuel enrichment" function for cold starts. I am assuming your Black Max has a fuel enrichment function like other engines used for cold starting like a "choke butterfly" used to be used on carburetor venturis. Activating the FE function is via the ignition key. You press in on the key, or you have a button adjacent to the key location on the dash board. Fuel enrichment solenoid is activated in the ON and Start functional positions of the key, be it a push in key switch, or a button adjacent to the key.
Your starting method is to set the engine to the vertical position with the tilt/trim and squeeze the fuel bulb till good and firm.
Then you push the button in the shifter and position the lever as I said above....45* toward the dash. (F gear disengaged)
You then turn the key to the ON position.
You then either push in on the key or push the button and hold for a period of time, maybe 15 seconds, maybe 30 seconds, depends on temperature and last time engine was run and how good it is primed from previous running.
Let the starter roll for 15-30 seconds. If it doesn't light off, wait a couple of minutes or so, squeeze the bulb to pump fuel back into the carbs and do it again.
Once you get it running and warmed up maybe 5 minutes, move out in the no wake zone in F gear and using the (assuming) knurled knob on the throttle linkage on the engine and set the idle RPMS to 675. There are other SS screw adjustments on the throttle arm(s) but they require a screwdriver to adjust...the probably "white" knurled, nylon knob is your clue.
After you get that done, your starting should be easier.
If you are on the water running the engine and it's warmed up and you stop and shut the engine off for a few minutes, turning the key to Start with the shifter in N is all you should need to do. The longer it sits, the less likely it will light right off.
In that case do the priming function listed above but once you push the key or button, roll the key on over to Start as i shouldn't need a lot of priming like first start of the day mentioned above.
If that fails too, they do your first start of the day procedure listed above.
If this fails you need to have a look at your engine and resolve what isn't up to "snuff".
