T9.9 Yamaha Idle problem

RatherBFishn · 07-11-2006, 07:32 AM

My 2002 T9.9 kicker just developed a problem last time out. It was running just fine then decided it did not want to idle anymore. I was backtrolling at about half throttle when this developed. The motor will start and run if the throttle is about 1/2 open but doesn't run perfectly. Back the throttle down and it stops. If the motor is cold it will start and run until the electric choke backs down and then it will stop. Notice some blue smoke occassionally at start up. Pulled the plugs...top plug perfect, bot plug wet. Removed the carb suspecting the motor was flooding. Did not notice abnormal debris in the carb, cleaned it and reinstalled. No change. This motor has run perfectly since new. Last previous use was 1 week ago crabbing at idle or slightly above for 3 hours. Worked perfect then. Of course it just went out of warranty a few weeks ago. It is stored upright on the boat transom, not tilted. I appreciate any help on this.
RBF

GSD · 07-11-2006, 07:43 AM

bottom plug wet? I'd try a new plug and see what happens.

Starfish · 07-11-2006, 11:32 AM

Check the oil level-- sounds like it "made oil" with gasoline in the oil and the level is too high. If the level is high, change the oil and monitor it to see if it continues to build up-- you may be running a little rich or not letting the motor get up to temperature before starting to troll. The symptoms you're describing are exactly the way my previous 8hp Honda used to behave when it acted up, before I had it rejetted and thermostatted.

RatherBFishn · 07-11-2006, 04:12 PM

I just changed the plugs. No help.
Then I removed the idle screw brass cap and played with the idle screw a bit. No luck there either.
The oil level is completely full and I think I can detect a hint of gasoline odor to it. Needs a change anyway so I will try that next.

RatherBFishn · 07-11-2006, 04:52 PM

Well, I changed the oil and filled it to about 4/5 full. Motor starts up and runs at a very fast rpm only. If it goes to idle it quits immediately. Played with the idle mixture screw again...no luck. Mystified.

Starfish · 07-11-2006, 05:42 PM

I hadn't noticed your other post about dunking the motor. Have you cleaned out the fuel filter and carb bowl? Also you might need to pull the idle jet and clean it out (use carb cleaner and poke it with a fine wire), it sounds like it might have gotten plugged. Was it salt water?

fishingls · 07-11-2006, 06:36 PM

I have owned two of the T9.9s-I always had to run a warmer plug in the bottom cylinder. If I didn't, I had idling problems. Go up one level at a time. NGK makes plugs for the 9.9 in hotter ranges. Most good auto parts stores can order them the hotter plugs.

RatherBFishn · 07-12-2006, 06:43 AM

The motor was dunked a few times with SALT water but looking at it with the cover off I don't see a lot of salt deposits. A little here and there but not tons. I did take the idle screw all the way out and it looked OK. I did not try to clean the idle port in the carb. I had the carb off the other day and cleaned the bowl and everything else with brake cleaner. There was a little gunk/corrosion in the very bottom of the bowl but not much. I guess I will take the carb off again and try to inspect/clean the idle port better. BTW this is my third T9.9 and this is the first I have had idling trouble. Thanks for your responses.

Chrome Bumper · 07-12-2006, 01:12 PM

Take the carb off, take apart, unscrew all the plugs, needles, seats so you can get a wire and spray carb cleaner in the tiniest passages, scrap it clean inside carefully with a wire. Probably still a little varnish somewhere. Boats.net should have diagrams online for you.

RatherBFishn · 07-12-2006, 06:59 PM

I guess 3 times a charm. I cleaned the carb once again, used a small wire in passages, sprayed about a ton of brake cleaner in everything, even in my eye. Now it runs and idles like a sewing machine once again. Never could see any FOD but it must have been there. Thanks for all the input.
RBF

Chrome Bumper · 07-12-2006, 08:35 PM

Yep, details details details. Musta set ya back about a buck 98 for that fix. The boat doc woulda got ya there.