Inselaffe
Well-Known Member
Hello,
I have an intermittent becoming constant problem with my 1990(?) white Yamaha F9.9AM 4-stroke outboard with a high thrust prop on my 22 foot saily boat, and thought maybe someone over here could throw some light on it for me.
It always starts perfectly, and runs smoothly, but after it had been run for some time (half hour - hour) and at high revs under load it would suddenly (suddenly as per as if a switch had been flicked) drop down to about half revs, then pop back up again.
This got worse over time, & it's now got much worse so that the motor won't rev up (sounds like its being held back with a low pitch 'mwwaaarrrrpppp' noise, not erratically misfiring) and only sometimes flicks up to full revs for half a second.
This may be a red herring but, to me (as a mecanic's son) it felt like an electrical problem because of the suddeness, so I tried pushing & wiggling the coil & CDI units, which used to usually flicked the motor back up to top revs. However, now the problem is worse this has no effect.
I have checked all the bullet connectors, and the earths I can find.
I took it into the workshop here in Lisbon & told them all this & during the 4 weeks they had the motor they just changed the plugs and 'played with' the carb & put it in the test tank for 30 mins under load (& charged me a fortune!) & when I got it back in the boat it was exactly the same
as before /forums/images/graemlins/frown.gif
Anybody have any ideas or suggestions?
I will take it back in to the workshop again on Monday, but would like to have some ideas before (Portugal is sunny, but incompetence unrealiability and laziness are the norm)
I have an intermittent becoming constant problem with my 1990(?) white Yamaha F9.9AM 4-stroke outboard with a high thrust prop on my 22 foot saily boat, and thought maybe someone over here could throw some light on it for me.
It always starts perfectly, and runs smoothly, but after it had been run for some time (half hour - hour) and at high revs under load it would suddenly (suddenly as per as if a switch had been flicked) drop down to about half revs, then pop back up again.
This got worse over time, & it's now got much worse so that the motor won't rev up (sounds like its being held back with a low pitch 'mwwaaarrrrpppp' noise, not erratically misfiring) and only sometimes flicks up to full revs for half a second.
This may be a red herring but, to me (as a mecanic's son) it felt like an electrical problem because of the suddeness, so I tried pushing & wiggling the coil & CDI units, which used to usually flicked the motor back up to top revs. However, now the problem is worse this has no effect.
I have checked all the bullet connectors, and the earths I can find.
I took it into the workshop here in Lisbon & told them all this & during the 4 weeks they had the motor they just changed the plugs and 'played with' the carb & put it in the test tank for 30 mins under load (& charged me a fortune!) & when I got it back in the boat it was exactly the same
as before /forums/images/graemlins/frown.gif
Anybody have any ideas or suggestions?
I will take it back in to the workshop again on Monday, but would like to have some ideas before (Portugal is sunny, but incompetence unrealiability and laziness are the norm)
