40 MARINER QUITS AT HIGH SPEED WITHOUT WARNING

SOURCE: engine won't run unless primer bulb is being pumped

I have the same problem and may have a solution. I looked at the primer pump and it was cracked letting air into the system. When I pumped it my finger was over the crack and it worked fine. When I stopped the crack was able to **** air again. Take a look.

SOURCE: Mariner 25 hp 2 stroke hard to start then quits and won't restart

It sounds like the float is sticking in the carb. Since the carb is higher than the fuel tank it pulls the fuel in by vaccum of the engine. when running at high rpms, it can burn the fuel thats flowing into the carb, when you idle down, the bowl of the carb is filling up with fuel faster than the engine can burn it and causing it to flood. Then when it shuts off at idle it does not want to start back up because it is flooded. To make a long stary short, pull the carb and give it a good cleaning and your problems should be solved.

SOURCE: 1984 mariner 5hp two stroke outboard wet sparkplug

Then it is flooding itself. You need to rebuild the carb and check your float level. Make sure to replace the needle and seat also because when they wear it will cause the engine to flood. I am 98% sure that will fix your problem!

SOURCE: outboard motor won't run under load

I have 1969 5hp Johnson. Starts and runs good, but will only push a 14ft row boat slow at low to medium rpm. When at higher rpm the the motor just revs up and the boat slows down to almost nothing just like it has seaweed around prop.Any help would be great.

SOURCE: boat won't plane

Check your prop hub. If you have a larger motor there are rubber bushings in the hub which can slip. This is a safety feature like shear pins. You may need to rebush the prop.

You also need the proper length motor for your transom. And you need enough power to overcome the drag and weight of a loaded boat. Check and see if the angle settings for the locking pin will provide an upward thrust to the hull and not plow the hull down.