40 hp 2 stroke open/close switch?

[branedge]

My son recently bought boat that came with 40 hp 2 stroke engine, sorry not sure if the year we think 2003. It idles fine but boggs down under full throttle. He has this switch open, which we think is a fuel enrichment switch. Could this be the issue? What is this switch

 

[racerone]

That could be the lever to open the " enrichment valve " ---A unit that has replaced choke flappers.----This suggests that the carburetors need attention.

 

[boscoe99]

That valve is part of the Yamaha Primestart system. An automatic fuel enrichment and derichment device if you will.

The valve is shown in the off position. Should be in the normal (automatic) position.

 

[branedge]

That valve is part of the Yamaha Primestart system. An automatic fuel enrichment and derichment device if you will.

The valve is shown in the off position. Should be in the normal (automatic) position.

 

[branedge]

Thank you. We've changed it to automatic (normal) what would running it in the open position cause?

 

[racerone]

Too much fuel would be going into the engine if valve is open.-----If motor runs better with valve open it points to a carburetor issue.

 

[99yam40]

run it in the normal mode.
open is to help get the motor runing if you cannot get it to start when in normal due to plugged up automatic system
once started in open you should turn it to closed or it will run too rich