1985 L6 115hp Merc runs rough 3/4 throttle

[bigdogbalog]

starts good and runs good from idle to about 3/4 throttle then starts to break down. good compression all cyl, good spark all cyl. carbs pulled and cleaned. one switch box was tested bad and both were changed as well as the stator. mechanic says timing is correct. which way do I go now ?

 

[jim dozier]

Re: 1985 L6 115hp Merc runs rough 3/4 throttle

Does manually choking partway help it. If so you are running lean and if the carbs are OK check the fuel pump and fuel lines.

 

[bigdogbalog]

Re: 1985 L6 115hp Merc runs rough 3/4 throttle

The fuel pump was checked and working fine. We are going to check the fuel lines back to the built-in tank and the vent line next. Thanks for your suggestion.

 

[bigdogbalog]

Re: 1985 L6 115hp Merc runs rough 3/4 throttle

Vent clear and gas line from tank to motor quick connect checked out ok. Going to do a rebuild on fuel pump....may be a weak diaphram.