force 120 loads up

[Crooked hook]

I have a force 120 motor that was running good. Right now the motor runs good at an idle, but once you open it up, it loads up and starts sputtering and, it only runs good for about 10 minutes. I already checked the timing and the spark, adjusted the floats, cleaned the carbs, checked the compression, and put new plugs in. What else could possibly be causing it to run like this?

 

[Jiggz]

Most likely you have broken reeds. And the only way to find out is by visually watching the carbs (without the air covers) blowback fuel when running. Or by physically removing the carbs and visually checking the reeds.

 

[jerryjerry05]

What year??​
They used 2 methods for choking the 90.
The old plunger type.
And the primer system.
The old usually no problems other than needing WD once in a while.
The primer has a diaphragm that can rupture and feed the carb too much fuel.
Or the fuel pump has ruptured the diaphragm ??

The primer, pinch off the line from the primer to the carb and see if that makes a difference??
Then take the fuel pump apart and check the diaphragm.

Also check the inline connectors and all the hoses.
Ethanol continues to destroy older hoses and fuel systems.

Depending on the year they might have installed a filter between the carb and pump??
If not put one in.

You check the fuel for water?
Install a fuel water separating filter.