Yamaha 40hp ignition problem

"hi to all.

i have this out

"hi to all.

i have this outboard engine ( yam,40hp 3 cylinder,2stroke,electronic ignition ) but i start it and it will only throttle to a fast idle (at idle upto very low revs,all is well ) when i put the throttle up a little more or above ( say a third throttle ) the engine studenly gets very lumpy.(almost like the choke has been put on ) ive put a strobe gun on it to check the timing and i find that when it does start to run lumpy the fireing becomes very iratic..

basicly as the enigine revs increase the strobe light gets faster as it should until i reach the revs/throttle ( aprox quater to a third of the throttle ) and on the strobe light the fireing of each cylinder becomes much less often.almost like it might only be fireing on aprox every 3 reverlution of the engine insted every of one revolution. plus ofcause each time the strobe lights up i can here the engine fire ( one stroke of power ) but its only fireing say aprox 3 times a second .

im almost cirtain its an electricle fault but i want as much advice as i can from any one who thinks they can help?????

i hope ive described it well enough

ive cleaned up the LT wires which were a bit coroded on all 3 coils,given the plugs a damn good clean ,im very sure the carbs are fine too,but still the problem persists.."

"Jeremy,

I would check the

"Jeremy,

I would check the main jets in the carbs. Yamahas have tiny orifices and clog easily.

Tony"

I am having the exact same pro

I am having the exact same problem with my Yamaha 40hp. It idles fine but about a third acceleration it breaks up on me. It was running fine until I was revving it up one day and then it started getting choppy. I dont think it is the carbs at all and I think it is in the ignition system. It feels as though the timing is off and it is misfiring. If any one has an idea please let me know. Thanks

hi jason.

i am very suspect

hi jason.

i am very suspect of the cdi unit on my engine so i have sent it to a firm with all the equipment for tests..
when i get the unit back ill update all my forums ive joined and let you know ..

Thanks for your response Jerem

Thanks for your response Jeremy. Is the CDI unit the Black plastic box mounted on the side of the motor above the throttle linkage with a small arrow that points to grooves or lines and one dot? Does anyone know how to adjust these. Is it done with a timing light and loosen or tighten the linkage rod?

hi jason.
just read your mesa

hi jason.
just read your mesage.
the cdi unit is on my engine atleast a black box and one of the throttle rods conects to the cdi unit (this advances and retards the ignition ) as the unit is also a cdi and advance/retard system.. not had any news yet on my cdi unit being faulty or not as the firm ive sent it too are testing when they can more for a favour. they say tho as its encased in a tar or resin goo this makes things alot harder..

the problem we had with our en

the problem we had with our engine was just the oil level swich braking down . weve bypassed it and the engine runs a treat now.
thanks for your help guys

Thanks Jeremy.... I may have t

Thanks Jeremy.... I may have the same problem. Where is the switch located? Is it on the tank for the oil injection? Im glad that you have it running so well.

"hi jason.
the switch is on t

"hi jason.
the switch is on the top of the tank behind the cap . think we just diconectd one of the wires. hope that helps..
we might also have a slighlt dodgy heat sensor as it looses power and almost misses if you keep it at full revs to more then say arox five mins, but let it cool for 30 seconds and its fine again"