J225 not reaching full power

[Incorrigible]

Engines: J225TXESS (1990 225hp)

Starboard engine is not reaching full power. At approximately 4000rpms engine begins to stumble, then recover, then stumble again, cycling every second or two.

I'm first starting to hunt down the cause. It sounds as though the engine is starving for fuel at higher RPM's. Engine runs well at lower rpms.

Thoughts?

Much thanks

 

[jonesg]

Re: J225 not reaching full power

When it starts breaking up, put a timing light on the cyl wires to see if its dropping spark to a cyl. Coils tend to break down under heat and load.
An examination of the sparkplugs might show the suspected cyl by an oily plug.