3.5 hp sears won't rev past idle under no load

[unior]

Have a 3.5 hp 1972 sears outboard that starts fine but won't rev right past idle. If I throttle up past idle it will rev a little/bog/rev a little/bog. The carb was cleaned out and I tryed fiddling with the float level. I replaced the spark plug. I tried adjusting the jet on the bottom of the bowl and it makes no difference in operation until the jet is so far in that the motor dies from no fuel at all. Adding a little or a lot of choke just makes it run worse. Should I check compression? I have no idea what numbers to look for. I'm somewhat stumped and need some input. Thanks in advance. unior

 

[unior]

Just for reference the engine is a tecumseh. Today after going over the carb again and just fiddling somehow it decided to take off and run almost perfect for a minute or two. Then it stalled and is back to it's old shenanigans. I pulled the flywheel and checked/cleaned the points. They look OK. I am wondering if the magneto is bad? Anyone? It so randomly ran great and revved to the moon for a couple minutes so I am suspecting ignition system.

 

[motorhead64]

This sounds carb related. When you remove the high speed jet/nut from the bottom of the carb, unscrew the needle and check the nut assembly....it has a small hole that enters near the threads. It needs to be clear. A very small diameter wire will fit through....or a small sewing needle. Some of these nuts have two holes. The other thing to check is the screen in the bowl chamber. Carefully remove the screen with a needle and clean it well...also the chamber underneath. Press the screen back in place when done. If fuel is restricted there, you starve under acceleration. Lastly, there is a welch plug on the outside of the carb body. A kit for this carb will usually include a replacement. If you remove the old one, it's not going to go back on, so don't attempt it without a part to replace it. Dirt behind the welch plug can also affect fuel flow. And finally, there is the little "duck bill" fuel pump apparatus that fits into the back of the carb throat. If it is cracked or stiff with age, it won't pump fuel sufficiently to allow high rpms. MH