misses at wot

[evolution6972]

i have a 1988 40 esg yamaha and when i am wot it misses i changed two coils going to get the last one this week if it doesnt fix the problem can someone give me ideas of what to check or maybe how to test stuff im afraid its gonna be the powerpack

 

[SparkieBoat]

Re: misses at wot

you need to learn how to dianose your motor instead of just throwing parts at it. get a DVA ($25 @ USA tools do a online google search) adapter, and follow this free diagnostic guide.
http://issuu.com/cdielectronics/doc...t.xml&backgroundColor=000000&showFlipBtn=true
you can check your fire while running the motor on the water with an inductive timing light. you may be having fuel issues. Once you can eliminate certain things it is easier to figure out your problem. follow the guide and feel free to ask any questions you may have...but at this point any suggestions would be pure speculation and could have you chasing your tail.

 

[99yam40]

Re: misses at wot

My C40 had a WOT miss and it turned out to be running too rich because a previous owner apparently drilled out the main jets( maybe trying to make a 50 out of it) after replacing with new ones it runs fine. A leaking fuel pump will put too much fuel into one cylinder also.
Not saying that is your problem, but you need to be sure it has good compression and spark on all cylinders and that the spark is not dropping on a cylinder or two before looking at the fuel.
An inductive timing light or tach hooked to the different plug wires can help see problems on the individual cylinders. And the light will show that the timing is correct or not
A Yamaha service manual and the proper testing equipment helps the most.