CONTINUOUSWAVE

[A unidentifed year and horsepower Mercury two-stroke-power-cycle outboard enigne starts, runs in neutral, and then stalls when its throttle is advanced.] Any advice is appreciated by this new boat owner. Had the boat out twice only to be towed in. Replaced battery, starter, primer bulb, and fuel hoses. The primer bulb is hard and gasoline is visible in filter. The engine appears to have some gasoline at bottom of engine upon inspection.

I had the same concern with my 1991 Merc 200. I increased my idle a bit and was able to get into gear without it dying. I ran a can of SeaFoam in a portable tank for a couple of trips and it all smoothed out and now runs fine. You may have your mid range jets plugged-up in the carburetor. Try the SeaFoam on idle and rev the motor without putting it in gear a few times for the carburetors to suck up the SeaFoam and see what happens

Does the engine accelerate at all in neutral? Or does it only stall when shifted to FWD gear?

Are you a good mechanic? Do you have the factory repair manual? Are you familiar with outboard engine service? If you don't answer yes, to all those questions, find a older mechanic who grew up with carburetor Mercury engines and hire him to work on your engine.

If you are a mechanic, then check for spark on all cylinders. A two-stroke-power-cycle engine will appear to run well at idle even if a cylinder or two is not firing. As soon as a load is applied it will stall.