Mariner outboard problem ?

[BillP]

A fishing buddy has a "new to him" 83 or 84 Mariner 25 with a problem I can't help with because I know nothing about that motor. When the motor is warm it starts rite up but then when you put it in gear and give it a little throttle it fades and dies. It seams to help if you start it with half choke and leave that on as you throttle up. What is the little knob in the choke button? is it the slow speed jet adjustment?

[Valv]

It's tough to figure out without more description, but sounds like carburator issues, needs to be cleaned up.

Compression can be a factor, have you done a compression test ?

Also coils could be a problem, they can give bad spark under load.

Post with more information of what you did to motor and we can see if we can help.

[Surface Tension]

If its dieing when you give it gas I'd suspect fuel shortage.

Check the gas line for cracks, loose connections and check the bulb. Check the fuel lines from he carb to the pump and then to the fitting. If there a filter replace it. Check the screen on the fuel pump. It be nice to know that both cylinders had good compression.

One question, after you choke and give it throttle does the engine eventually build RPMs and if so do you need to continue to choke it? If yes and the above suggestions don't work I'd be looking at cleaning the carb then go onto replacing the diaphragms on the fuel pump.