I got a Merc 9.9 unknown vintage, electric start, remote control... with a small 8' power-race boat which I am told normally takes 25-40HP motors.<br /><br />The motor would die at anything much above idle speed.<br /><br />I have replaced all internal fuel lines from external fuel coupler to filter, and from filter to carb.<br /><br />I have cleaned out the fuel filter (looked like small rubber particles on both sides of the mesh screen).<br /><br />I have added an inline glass see through filter body (same as marine or auto store) to the fuel line from the external tank after the primer bulb.<br /><br /><br />I flooded both the carb intake, carb bowl, and choke knob intake with carb cleaner and let it sit for a half hour.<br /><br />I have started the engine and let it run off the carb cleaner in short amount of time.<br /><br />The previous owner told me that a carb rebuild and water impellor was replaced before I bought the engine (who knows!)<br /><br /><br />Now I have reclaimed the throttle control from idle to just over 2/3'rds rpm although occasionally it will quit after running at idle speed for a bit.<br /><br />The current big problem is that there is a RPM range just over 2/3'rds throttle where the engine will slow down and die. Moving the throttle control back towards a lower RPM or into the idle will not help the engine recover.<br /><br />I have been able to keep the motor going at high rpm with a little CPR (pumping small rapid pulses on the primer bulb).<br /><br />I was suprised that I couldn't get on a plane at full throttle so I may need to get a new motor anyway in the 25-40 range but I still want to give this Merc a chance.<br /><br />Any ideas?
