Yamaha 9.9 over revving

[maninahat]

Hi all.<br />Yes, OK, it wasn't a good idea to lend the boat to my son in the first place but....<br /><br />I got a call "there's something wrong with the engine".<br />It was revving as if it was at almost full throttle.<br />The idle screw is about half an inch away from making connection with the rod, so it can't be adjusted downwards.<br />I'm guessing the choke could be stuck open but thats a guess and I don't know how to fix it if I'm right.<br />There's a fair bit of evidence that they hit something pretty hard, probably going backwards, but claim not to have noticed anything.<br /><br />Any ideas please (other than "Don't lend your boat to your son" - that goes wothout saying.)<br /><br />Cheers

 

[jim dozier]

Re: Yamaha 9.9 over revving

Pull the hood and work the throttle. Look to see if the linkage where it connects to the carb butterflies and where it connects to the ignition timing is correct. At idle the carb butterflies should be against their idle stops and the igntion should be against the low speed stop. At full throttle they should be against the high speed stops and the carb butterflies should be all the way open. Sounds to me like a linkage problem. I don't know that particular engine but I once had a Johnson 9.9 that had a tooth missing in the tiller handle joint and would sometimes jump a tooth and not let the engine throttle all the way up, it could have just as easily prevented it from idling also.<br /><br />How else is the boy going to learn to fix engines if you don't let him break it once in a while

 

[maninahat]

Re: Yamaha 9.9 over revving

Thanks.<br />I'll give it a go at the weekend and let you know.<br />Maninahat

 

[maninahat]

Re: Yamaha 9.9 over revving

Success!!!!<br /><br />I disconnected the throttle linkage, unscrewed it about 5 turns, reconnected it - the throttle stop was then touching where it shuld and it purrs like a cat. <br />Actually that's the abridged version. I had to take the carb off and all sorts. Still - done now. <br />Thaks a bunch jimd.<br /><br />All I've got to do now is fix the steering.