Hi all I have been reading many post but i couldent have find any one that have had the problem that i have.

If you take the volts reading from the battery with the engine off the readings says 12.8 volts but if i run the engine and take the voltage one more time the readings are moving from 12.6 to 0.

Another thing if i push the throttle slowly from neutral when y get half the way to full throttle the engine dies (i loss the spark) but if i go all the way to full throttle very fast the engine works great, it stalls alittle but it works i also can go back on the throttle with out any problem and go back up to full throttle with out any problem.

By the way this engine is a 175 hp Mercury 1990

If any one has any idea please let me know.

Thanks alot from Mexico

Francisco

If battery voltage drops to 0 then it's a bad battery. A hesitation problem is usually dirty carbs.

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I do not know what year or hp your motor is. But what you have described matches mine to a "T". I cleaned the carbs and checked all other fuel items. Carbs were as clean as new. Other items fine.
Put back in water same result. Then it completely stopped firing. I hooked up timing light and found no fire on any plug.
I checked the ohms on the rectifier and it fails, checked the ohms on red & blue wire from stator to switch box and the red one fails.
Expensive parts, but it sounds as if we have the same problem.
I do not think the problem is fuel related.

this might help you guy www.cdielectronics.com - /downloads/troubleshooting guide might also check you kill switches,or killtilt kill switch hope it helps.