Mariner 8 hp two stroke problem – dieing when open throttle

[GART]

Next problem, since it overheated my Mariner 8 sometimes will not rev above a fast tick over, not always, just when I need it! When I open the throttle the engine dies, if I close it, it sometimes keeps running. It starts again perfectly immediately as long as only fast tick over, even after being left for two weeks it started first time, once I managed to get it to achieve higher revs by pulling out the choke while on fast tick over then putting it in before it died, then opened the throttle and it worked fine. But the next time I tried this it did not work. This indicates a fuel problem, however the wires from the magneto look dark and discoloured after the overheating problem. The Mariner is the same as a Yamaha 8.
Any Ideas?

 

[alan17]

Sounds like dirt in the main jet in the carb. Should be simple enough to remove carb. Strip to gain access to main jet and check for any obstruction. Do not clear by prodding with wire. Jet orifice is very small and wire will enlarge the hole causing an over rich mixture. Try blowing any dirt out by mouth (nasty taste!) or an air line (keep a firm grip on the jet) If you must prod it clear try a bristle from a stiffish brush.

 

[wells01]

Hi
It could be water in the float bowl . It just lays there until you open the throttle, then the main jet drags the water up and puts the spark out. As alan17 suggests a strip down is in order.

 

[Clyde_Wanderer]

Is it running from an external fuel tank?
If so it may be the pump diaphrams on side of carb.

 

[gandy]

[ QUOTE ]
Hi
It could be water in the float bowl . It just lays there until you open the throttle, then the main jet drags the water up and puts the spark out. As alan17 suggests a strip down is in order.

[/ QUOTE ]That's exactly what happened with my Merc 2.2. This was after I'd fully cleaned the carb and fuel system. You may have a drain screw on the carb bowl, in which case you can quickly see.