not maxing out

[mistercinder]

I have a 1999 mercury 50 four stroke four cyl - it won't max out but hits a flat spot at half throttle and that's it - auto choke works and green/white wire is connected to the CDI - am using fresh fuel, new plugs - cambelt timing is correct, carbs are clean - it seems to be carb mixture/balancing? - to richen do I unscrew the brass idle screws and do these affect the rest of the mixture range?

thanks

 

[Docksidemarineservices]

Replace the fuel line from the tank. The inside liner has probably collapsed causing a slight fuel restriction.

 

[mistercinder]

new fuel line, tank and bulb - fuel is hand pumping thru to fuel pump inlet - could it be the acceleration pump? or fuel pump? carbs clean and set up - we're being overtaken by rowing boats and getting increasingly pissed off!

 

[racerone]

Always start with the most basic stuff.------------------DO A COMPRESSION TEST.---------Costs nothing to do if you have a tester. if not they are a mere $30.00 at the store.---------------Check that you have spark at each cylinder that will jump a gap of at least 1/4" with a snap you can hear.