carb problems

[toeknee dee]

I have a 89 70hp yamaha how do you determine which carb is giving you a problem? how can check your fuel pump?

[Ken]

dee,
With motor idling, you could squirt some fuel into the throat of each carb one at a time to see which one made the most difference. Or you could remove a spark plug wire from each cylinder to see which one is most weak.
If you suspect carb problems and it has been at least five years since last overhaul, it would be best to remove, teardown, and install a carb kit.
You could pressure test the fuel pump, or disassemble the pump and inspect the diaphrams per the manual. A lot of outboard owners just replace the fuel pump every five years.
You really need a Yamaha service manual to guide you along for the above procedures. You can order online at www.yamahapubs.com.
Good luck [img]smile.gif[/img] ,
Ken K

[jb123]

yes, either the fuel spray, pulling plug wires or try manually choking each throat with your finger,etc, to isolate.that is assuming you have good fuel supply and spark.

[toeknee dee]

I had just picked up this boat it appears that the gas was contaminated.I ran it on a spare tank and it ran alot better.I notticed the middle carb had tapped gas comming out the mouth.I tapped the carb and that may have freed up the float because I don't see that any longer.I changed the plugs and the spark is fine.When I rev up the motor and go back to idol it will want to stall.