Losing Power Yamaha 250 EFI

[lovesfishin]

I have a Yamaha 250 EFI and I have no power. At full throttle, the engine runs at 3300RPM. My mechanic checked the coils and indicated to me that cylinder 5 is not recieving any fire. He has indicated it MAY be the CDI but told me he would check everything else and leave the CDI as the last resort. He informed me that the CDI hardly ever go out.

On the way in from fishing trip, the engine DRANK the gas and would only go 24mph barely planing (we had to shift weight to front of boat). Normally runs around 46mph at top end. It was acting sluggish that morning and then after *****ing for a while NO POWER.

Is there anything else that can cause this and we should check before I purchase 900.00 CDI unit???

[jb123]

what year efi, if it has an o2 sensor, have it checked.one cylinder not firing wont have an effect on fuel usage but a sensor will.you should also check your primary pumps as they could be bad also....did you see any unspent fuel out of prop while running??

http://www.boatsetup.com/O2sensor.pdf

[lovesfishin]

Thanks. It is a 2001 and it does in fact have an o2 sensor. I will let my mechanic know about the o2 sensor. Does this sound like an o2 sensor problem or a cdi problem? No uspent fuel.

The day the boat went out it was sluggish and then went completely limp. Is this indicative of an o2 sensor?

[jb123]

my exp with a clogged or bad o2 is not able to reach max rpms, maybe about 1200 less.

[tunaboy]

Are you sure the problem is with the spark-plugs. The reason I am asking is because I had exactly the same problem and symptoms and it turned out that one injector was dirty which led to soaring fuel consumption and loss of RPMs.