40 HP Yamaha acceleration problem

[brian gillespie]

I am having a problem with my 40 HP 2004 Yamaha 4 stroke.

It starts and runs well on idle and up to about 1200 rpm.

When I accelerate the engine it seems not to fire on all cylinders ( IT shakes) through about 1500 rpms - then it runs fine as the boat comes to plane.

There are 3 carburetors ( 3 of them) which have been cleaned twice!! but no real improvement -- also have put a Yamaha water separator on the fuel line to reduce ethanol issues as well as putting stabilizer in the gas.

Has new plugs.

Also the carburetors have been synchronized and carburetor cleaner added to the gas.

Engine runs better but still shakes when it is accelerated to get on plane. It does not seem to be getting enough gas.

Any ideas??

 

[racerone]

We see this all the time -----" carburetors have been cleaned twice " and even 3/ 4 times.---------------There are very small passage ways in there that must be verified clean , which means taking the carburetor all apart.-----------Often see people say " finally took advice and took carburetors all apart for a good cleaning. Now motor runs like a top.--------------You must also verify compression and strong spark on all 3 cylinders.

 

[brian gillespie]

Is there a good self instructional video on cleaning a Yamaha 40HP 2004 carb??

 

[justintime]

you need to sync them and make sure you have spark on all 3 cylinders

these motors do shake