50hp Yamaha problems

[<Cliff>]

I have a 99' 50 hp yamaha. The problem is that the motor is backing the rpms off while I'm trying to run at full throttle. If you release the throttle then get back into it, the motor will correct itself for a little while, then do the same again. It is very frustrating. The motor has been tuned up, fuel filter changed, carps checked & adjusted to factory specs. None of this helped. Starts & runs great at low speeds. Mechanic cannot figure it out. He said to try squeezing fuel bulb while this happens, but did not help. It just kept loosing rpm's till it finally dyed.

[<boats.net>]

You will have to troubleshoot it on the water, Fuel or Ignition can cause that if the fuel system is ok then test ign. and since the timming is controled by the CDI on that engine keep a close eye on timming

[<David>]

I have the same problem with a 99' 40 hp (C40TYRY) while running full throtle the rpm's decrease dramatically. If I return to neutral then back to full throtle it runs fine for a period of time. While the problem is occurring, tapping on the linkage (at the CDI unit) that connects to the CDI causes the motor to return to full RPM's. Does this indicate a bad CDI unit?

[<jayg>]

I have a 50ETLK 1985 and it is giving some problems. Cylinder 2 and 3 are not getting fire however; if I test each coil by it self it will fire. If I switch the coil connections around all fire separately. If they are connected in sequence 2 and 3 will not fire...any suggestions? I'm thinking the powerpack or stater.

[Rustysa]

I have a 2000 C40TLRY doing the same thing you guys are describing, I've changed my fuel lines, filters, tried premium octane fuels... no luck. Yesterday I ran it with the cowling off, held the carbs @ WOT with my hand and back off of the throttle @ my control box, as soon as it got to where it barely moved the linkage @ the CDI box, the motor immediately sped up and began running as it normally would. Sounds to me like Yamaha had a bad batch of these CDI units, this isn't the only forum I've seen describing the same problem with the 40-50 hp motors within the 99-00 year models. I'm just hoping that the extended warranty covers this if it infact cannot be adjusted or repaired.

[<yamaha racer>]

had the same problem but mine was the high speed jets in the carbs.

[<Rocky>]

New CDI will fix that rpm going away for no apparent reson.

[<Norman GB>]

Hi,I have a 25hp yamaha 99 with less than 150hrs running time.The cdi unit died,no slowing of engine.Contacted yamaha uk and was told every thing wears out so there was nothing they could do to help out.Local repair shop have had a similar prob on a 50 , bad starting intermitent running.Maybe there is a faulty batch of 99-00 cdi units.At £280.00 I hope replacement last a little longer.Should yamaha recomend carrying a spare unit in case yours wears out?.