YAMAHA 9.9 dies beyond idle

[gybe98]

Guys, great forum, keep up the good work!!<br /><br />I have a 1987 Yamaha 9.9HP 4-stroke. Starts and idles fine until I try to give it more fuel. Once I do that it sputters and dies but starts up fine after that. <br /><br />I've rebuilt the carb and recently replaced the fuel pump, fuel filter, tank and lines. <br /><br />I suspect I should check to see if the needle valve is sticking, but what should I look for other than that?<br /><br />Thanks for all your help.

 

[Ray Neudecker]

Re: YAMAHA 9.9 dies beyond idle

Did you reset the air screw when you rebuilt the carb? Having replaced the rest of the fuel system, you have all the symptoms of a carb problem.

 

[gybe98]

Re: YAMAHA 9.9 dies beyond idle

I reset the screw to about 8 turns, which is where it was initially set. After that did not seem to help, I started to adjust it in the hopes that maybe it was incorrect. However that has not seemed to solve the problem.<br /><br />Any more suggestions? I really appreciate the help.

 

[jim dozier]

Re: YAMAHA 9.9 dies beyond idle

I don't know that particular engine and carb but I am willing to bet that 8 turns out from lightly seated is not spec. Go to the bottom of this web page and buy a manual for your engine. I agree that you have all the symptoms of a dirty carb. If its idles OK, you probably have crud in the main jets. That's why it can't get off idle. You wouldn't be the first to do an inadequate job of cleaning a carb. Its not a beauty contest, you need to clean the orifices with carb cleaner and compressed air, and install a rebuild kit.

 

[Grant S]

Re: YAMAHA 9.9 dies beyond idle

I see this is an old topic, but I had one of these with the same symptoms, it turned out to be a low oil pressure cutout. There will be an oil pressure sensor in the side of the powerhead, try disconnecting this breifly and see if that improves things. If it does, dont run the engine for any length of time or you will ruin the crank and bearings.

 

[jim dozier]

Re: YAMAHA 9.9 dies beyond idle

Did Yamaha or anybody besides Honda even make a 4-stroke outboard in 1987?