raykeion64
New member
hi i need help. I'm a boat mechanic and I've never ran into this problem before. i have a 1989 175 mercury blackmax that dies at full throttle. if u press gas peddle and ease from idle to full speed it will bog down at midrange speed. the only way it will get pass mid range speed is to choke it. i have recently found out that i can get it to go full speed if i press the gas peddle down kind of fast then it will go full speed. if i let off the gas peddle just a little at full speed the motor will shut completely off. i can however, have to keep tapping the gas peddle to ease down from full speed so the motor won't shut off. it runs very good at idle and before i get to midrange speeds it runs perfect. the only way it will go full speed is if i press the gas peddle fast, it won't go to mid range of full speed it i press the gas pedal slow. compression is 120 psi on all cyl, rebuilt fuel pump,cleaned carbs twice and i even set the floats just a little pass level to it can get more fuel,timing advance arm is moving and advancing perfect, also use new fuel line and new tank,still doing the something. perfect blue spark on all cylinders its jump my spark tester gap. the motor is on a 1989 18 foot 4 champion bass boat. the outboard motor does have one of those props with the hole in the side of it. i guess its for faster take off. i think the motor is a 25 inch shaft. they have it mounted on the 3rd hole on the motor i guess it was to lifted motor up some so it wouldn't have a hard time planing out. the bottom of the outboard is about a 8 or 9 inches past the very bottom of boat. please help me with this problem I'm having its getting agervating thanks a lot.
