yamaha 9.9 runs only on full choke

[yamaboat]

I have a 1990 2-stroke electric start outboard that for some reason it will only run when in full choke. When I take it off choke it sputters and then dies, like it does not have enough air. After about 30 minutes on choke it will also start having power problems. I cleaned the carb. and it looked fine. This did appear to be a gradual increasing problem and did not happen overnight. Any suggestions would be greatly appeciated.

 

[31900]

Re: yamaha 9.9 runs only on full choke

G'Day Yamaboat,<br />I see that this is your first post. Welcome. There are many people on this site that can give you good advice but it pays to give the model number of your motor when you ask a question. I have found from reading the posts on this site that you will get an answer from the experts telling you that you have a carburettor problem and while you think you have cleaned it well, it needs soaking and blowing out with compressed air because the idling circuits that have small jets and passages are most likely still blocked. try to give some history like how long since last used or stored and when symtoms began etc.

 

[rodbolt]

Re: yamaha 9.9 runs only on full choke

you still have a carb problem. how and when did this problem occur? when you take the choke off it dies from lack of fuel not air. could be not enough fuel in the bowl could be clogged jets. but by applying the choke you restrict air,increase intake vacum and force the mix rich. on rare occasions you may have a bad reed. I have never seen a bad reed on a small yamaha but its possible. usually its trash in the carb.

 

[31900]

Re: yamaha 9.9 runs only on full choke

I thought Rodbolt would get on this one. He is one of the best. Take his advice and give some more info on model/HP, fuel condition etc. Sock it to him rodbolt.

 

[yamaboat]

Re: yamaha 9.9 runs only on full choke

Originally posted by rodbolt:<br /> you still have a carb problem. how and when did this problem occur? when you take the choke off it dies from lack of fuel not air. could be not enough fuel in the bowl could be clogged jets. but by applying the choke you restrict air,increase intake vacum and force the mix rich. on rare occasions you may have a bad reed. I have never seen a bad reed on a small yamaha but its possible. usually its trash in the carb.

 

[yamaboat]

Re: yamaha 9.9 runs only on full choke

The problem happened after having my boat on the lake for about two weeks. I might not of ran the gas out of it (not sure if that is needed evertime). My carb. cleaning skills are novice, at best. I used stp carb cleaner and just sprayed everything. Do you have recommendation on how best to clean. Thank you very much for your quick response.

 

[rodbolt]

Re: yamaha 9.9 runs only on full choke

completly dissasemble the carb. check all passages and blow each out with air and carb spray cleaner. if you buy a soak tank dont soak it more than 20 min or so. remove the main jet and nozzle assy. if you look closely you will see the idle fuel pickup passage. try to drain the carb in a clean container to check for water. water and trash are the normall causes. while the carb is off you can inspect the reeds for broken ones or debris. but usually its water or trash in the bowl. buy a manual or at least look at a parts breakdown. make sure the needle seat and the area under it is clear.

 

[yamaboat]

Re: yamaha 9.9 runs only on full choke

I will do that this weekend and let you know. Thanks.

 

[ianyoung77]

Re: yamaha 9.9 runs only on full choke

Yamaboat,<br /><br />I recently did my carby for the first time and as always rodbolt is on the mark. I emptied my float tank onto white paper towel and found rust in the fuel which led me to other problems elsewhere. I used spray carby cleaner which worked well, however, it is a good idea to wear safety glasses as it often comes back at you. You can also get compressed air in a can although I just used my mouth - not pleasant but I'm still breathing. Just make sure every passage is clear and works ok and I's sure it will go fine.

 

[rodbolt]

Re: yamaha 9.9 runs only on full choke

the safty glasses is a wonderful mandatory thing. sorry I forgot about it. but yes carb leaner in the eyes will make your nose run at the very least. it is painful.

 

[yamaboat]

Re: yamaha 9.9 runs only on full choke

OK. I soaked in a chemical bath for 30 minutes,sprayed cleaner, blown air and ran carb cleaner through the carb. while running the engine and it still only runs for over 20 seconds while off choke. <br /><br />It runs off choke for about 20 seconds on idle or even running at high rpms and then it stalls. If there was constriction, would it have problems at high rpms off choke? Still searching.

 

[rodbolt]

Re: yamaha 9.9 runs only on full choke

do you understand what the choke does ?

 

[yamaboat]

Re: yamaha 9.9 runs only on full choke

I understand only enough that it allows less air in the intake which gives the engine a richer mix. <br /><br />The fuel bowl and the all components appear to be very clean. I used b-12 chemical for soaking. I blew out all the holes with air. I did notice that the tube that runs through the middle of the carb. was slightly at a angle, but it was clear in the middle. <br /><br />I agree with what rodbolt is saying, it does appear to be running out of fuel and as soon as push the choke, it kicks back in. After the chemical bath it was splotless. I did learn that if you put the float bracket on backwards there is a release hole for fuel to squirt through. (ha ha, well not really)<br /><br />I bow to everyone's knowledge base on this. Should I try cleaning it again or just call uncle and have a professional fix it? Better yet, get a new carb, it will probably cost the same.

 

[bigbrownbuku]

Re: yamaha 9.9 runs only on full choke

try hooking your gas line striaght to the carb and keep it primed. kinda sounds like a delivery restriction.

 

[rodbolt]

Re: yamaha 9.9 runs only on full choke

if the level in the bowl is low the choke will be required to enrichen the fuel mix. but that 9.9 will run several minutes on a bowl that was filled with the primer. I still think its a delivery problem in the carb circuits. yes by closeing the choke your restricting air. by restricting air the carb main and idle circuits are bypassed and the fuel mix is forced rich.<br /> I have a 15hp with a locked power head that Ill try to have a look at the carb and give more info. I dont have the circuit layout by memory.

 

[yamaboat]

Re: yamaha 9.9 runs only on full choke

Rodbolt, I have a diagram of the carb. that I can fax or email you offline. Also, it does happen at higher rpm's. I do a count of 20 to 23 seconds consistently before it dies. I thought maybe the fuel filter was clogged, but discounted that by bypassing it for a test.<br /><br />You are right, when it is running well it takes a good 5 minutes to run the fuel out of the bowl. It has to be within the carb.<br /><br />Good learning experiend for me. I appreciate your help.