92 Yamaha 9.9 4 stroke carb ?

[ferro762]

I just got this motor, not sure how long it sat before I got it. Before I rebuilt the carbs It would run but only if I keep my hand over the intake to choke it. I cleaned the carb and it ran without me having to choke it but not strong. Then I rebuilt the carbs and it goes back to running only when choked. The fuel pump is working, the lines look good. The motor is very clean for being a 92. Now in the diagram below there is one thing I didnt pay attention to before messing with it. The #5 Pilot Jet drops into the throat of the carb, the part that hangs down is a 1/2 cylinder to were when the gas goes through, it would force it to a certain direction rather then just strait down. My question is which way should it face, towards the intake or going into the engine? While cleaning and rebuilding i forced air and carb cleaner into every orifice and cleaner and air came out another side, so im pretty sure it's cleaned out. Also, how should I adjust the air valve? is there anything else to adjust to help it run better? ive moved the valve in and out and it doesnt seem to change the way it sounds or runs. I now have 2 motors apart in the garage and I just want to get out and fish, any help would be really appreciated. Thanks.http://www.boats.net/parts/search/Yamaha/Outboard/1992/T9.9EXHQ/CARBURETOR/parts.html

 

[msb466]

Re: 92 Yamaha 9.9 4 stroke carb ?

I am experiencing the same problem on a 2002 15 hp 4 stroke. I feel your pain. I have pulled the carb 10 times to try and adjust it. I am also trying to figure out the jet question.

Post your solution if you figure it out!!!!

 

[ferro762]

Re: 92 Yamaha 9.9 4 stroke carb ?

will do

 

[msb466]

Re: 92 Yamaha 9.9 4 stroke carb ?

Got it running.


For me it was the air mix valve. Talked to a master tech at length. I needed to remove an EPA mandated brass plug to get at the air mix valve. You have to drill, tap, and pull out the plug to get at the mix valve on post 1998 carbs.

The techs manual stated that you need to be at 3 turns out from full closed on the air valve for a 1998 9.9 hp 4 stroke. 2.5 worked for my 15hp 2002 4 stroke. I had to clean the carb one last time to make sure...

My throttle linkage wasn't adjusted right either. Twisting the tiller throttle did not advance the throttle on the carb correctly. Twisting the throttle in neutral resulted in no real change in RPMs and no visible change in the throttle position. After adjustment at the carb end, things started working.

Your questions about the main nozzle, pilot jet were answered by the master tech. They are NOT directional. It doesn't matter which direction they are turned.

 

[duckpond49]

Re: 92 Yamaha 9.9 4 stroke carb ?

Similar problem with an '87 4 stroke carb. It's an elec. start remoted engine but will only start with my thumb choking the intake. Will settle down and run fine and then after about a minute the "plunger" drops and it settles into an idle. Wants to stall on acceleration and wants to stall when dropping down from high rev.
I've had the carb apart and cleaned every nook, jet, passage and cranny. That got it running better but hasn't solved the cold start problem.
I have a service manual but it doesn't explain how all this works. Just tells you how to take it apart, inspect and reassemble. The troubleshooting guide is very cryptic. "Plunger spring broken?> No.> B.V.S valve replace?> No>. Replace carburetor."


I looked on the web for a used carb, (they want $450 for a new one!) and I see lots of motors going for way too cheap saying "runs but the carb needs cleaned" so this sounds like these carbs are chronic trouble.