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2001 Yamaha T9.9 EXHY 4 stroke stalls after 15 minutes of operation

rdtrout

New member
I have had this in the shop 3 times now for this problem, after 15-20 minutes of operation engines stalls, acting as if it is out of fuel, pump the fuel ball and it restarts, runs only a few minutes and stalls again. Engine is on its own, spin on filter out of the main tank, we have replaced filter, fuel lines and squeeze ball, no cure as of yet? As well as other engine work done by the dealer.
 
I'm interested in the answer to this post as my Yamaha 8HP long shaft has recently (this weekend) developed the same problem. We put in in the water Friday evening and it ran perfect. Saturday morning, perfect. Coming back Saturday afternoon, we tied up to the fuel dock and was preparing to get the boat ready to pull out. After idling for about 6 minutes, purring like a cat, it died. I pumped the fuel bulb and got it to restart. I went and backed the trailer into the water and came to retrieve the boat to find that the engine has quit again. I pumped the fuel bulb and got it to restart. I backed away from the pier and shifted to fwd and the engine died and would not restart. The boat was backing towards the breakwall where we tied up. The breakwall is like a little island not connected to anything else. Now we had a truck/trailer backed into the water and were sitting on a boat tied to an island with an engine that would not restart. I unplugged the fuel line, full choke and rolled the engine over. Then reconnected the line, pumped the fuel bulb and no start. Let it sit for a few minutes and "presto", the engine started and operated perfectly for short run to the ramp. It idled fine at the ramp. I did all the simple fuel checks and found nothing. I have recently replaced the entire fuel line system which has worked flawlessly for months. Wondering if I have a fuel pump problem? Please keep posting as you trouble shoot your problem. John
 
One more thing. I was thinking that I had a fuel pump problem but I could also have a small vacuum leak that is affecting the fuel pump at low rpm. What do you think?
 
That could be possible? I have an appointment with another Yamaha technician this Friday to look at the engine, I will keep you posted!
 
after taking in my engine, the mechanic could not imitate my problems, although he cleaned and adjusted the carb. He said another fellow in the shop had a similar experience years ago though, it was detected that where the fuel stem comes out of the fuel tank, there is typically a anti-syphon valve where the fuel line connects to, this valve can get sticky and not work properly, it needs to be taken apart and cleaned with carb. cleaner or replaced. I also asked about the possibility of a vacuum leak causing the fuel pump to act up, most fuel pumps are mechanical and not run by vacuum, but he did say that if the breather line for the crankcase was plugged, it could effect the diaphram operation of the fuel pump causing it to malfunction. Hope this gives some direction for you.:)
 
When was the last time you cleaned the carb??? Stop using low grade gas - use only premium. Look in your fuel tank for water - shows up as dark spots or a layering effect - if so drain tank, clean carb and have fun.
 
Whap happens when you operate the manual fuel pump ???--------------------Also it is a good idea to run these motors out of fuel if they are going to sit for some time-----Keeps the carburetor from gumming up.
 
i am interested in the findings of this problem. i have a 9.9 2000 and it runs great as long as im just idling but after 10-15 min of full throttle it stalls at the ramp and will not restart till it cools down. techs cannot repeat the problem, temp is good. the last tech that looked at it did some research and found there were problems with the carb from factory mold that contributed to a crack when they get hot. this sounds like a reach to me and i dont want to throw 300$ away on a carb if it is not going to fix it.
 
I had a similar problem, the tube inside of the clamp inside of my tank was loose and after a while would loose its prime and the engine would stall out. Also had the rubber hose with the filter end fall right off of one of my older portable tanks. I'd pump the bulb, the motor would start up and run until the fuel in the bulb was spent.
 
try running on portable tank eliminate you tank as problem. remove fuel connectors place line directly in tank thru fuel fill on portable tank connect directly to engine at fuel filter you may need to cut a small length apx 1inch of the engine full line place on inlet nipple of fuel filter this will help when you hook primer bulb line to filter this shim will allow for a airtight connection. try holding primer bulb in vertical position while running. vent open on tank? post results
 
ThiI also have a Yamaha T9.9 as a kicker on our sailboat. The first year the engine worked great. Then it started to stall after running for about 30 minutes. It will restart but will only run for progressively shorter time on each restart. It has been back to the dealer from whom we purchased it. They say in had old gas and a gummed up carborator. This would be logical but the carborator is run dry at the end of each day and the gas was fresh, less than two weeks old. We only burn marine gas without ethonol. When it reaches the point where it will not restart I can pull the input gas line from the fuel pump. This seems to release a lot of pressure. When the gas line is reinstalled the engine will restart and then the process starts all over again. The Yamaha dealer does not seem to be interested nor inclined to want to spend any time resolving this issue. Any input or ideas would be very welcome.
 
i used mine for the first time in over 7months adn it started on the first pull. all i was doing was idling for about 30-40 min. then it quit and like always it wouldnt restart for about 20 min. i need to trade the damn thing. im sure its not the fuel tank.
 
Could be the ignition coil(s) ... The engine will start and run fine until it starts to get hot under the cowling. As the ignition coil(s) heat up, they will start to fail and then can drop out all together. Let it cool down again... it will start fine, run fine and then do the same thing all over as it gets hot under the hood again. Tough to diagnose because we all check by pulling plug wires when it is on the trailer and the engine is cold. Don't toss an entire engine due to a failing coil!
 
thx deepsea21, i had a lawnmower that i fixed once that had the same symptoms. new coil fixed it. why didnt i think of that? anyone know where i can find one? i hate to spend much $ not sure of result and the one web site i checked was 70 bucks. if anyone knows the best place to find parts let me know. F9.9MSHY 2000
 
I have had this in the shop 3 times now for this problem, after 15-20 minutes of operation engines stalls, acting as if it is out of fuel, pump the fuel ball and it restarts, runs only a few minutes and stalls again. Engine is on its own, spin on filter out of the main tank, we have replaced filter, fuel lines and squeeze ball, no cure as of yet? As well as other engine work done by the dealer.
This happened to my friends boat. Turned out to be the coil. When it got heated it would kill the motor.
 
Well, before you start buying coils... start the engine up and let it run until it dies per your symptoms. Then quickly take off the cowling, pull the plug wires from the plugs and stick a nail or a bolt or something metalic up in one of the plug wires, hold it with something non-conductive such as a wooden clothesline clip so you don't get a good jolt and then have some one turn the key/ pull the starter rope while you hold the nail closer and closer to the engine block... you should see a spark jump from the bolt to the block around 1/4 inch. If not... it is probably the coil. You'll want to do this quickly though so the coil doesn't have time to cool down when you have the cover off and it mysteriously fixes itself again.
 
I got a new coil and just now getting around to replacing it. (I have 3 boats). it did not come with new plug connectors. it appears I will have to damage the insulators to get the new wires. if anyone has done this before and knows a trick please chime in.
 
My 1999 9.9 had a fuel (vapor lock) problem -- replaced the pump with new model (water jacket base) -- no problems after that.

However -- something new:
My 703 remote control/9.9 Yamaha has been reliable until a few days ago. There may have been a wiring issue, but I thought everything was OK. Starter solenoid failed after a few funky starts, but after the solenoid was replaced the engine idles fine, but will not rev up -- either in fast idle or in gear. It just bogs down -- it seems the timing changes ...?
 
My 703 remote control/9.9 Yamaha has been reliable until a few days ago. There may have been a wiring issue, but I thought everything was OK. Starter solenoid failed after a few funky starts, but after the solenoid was replaced the engine idles fine, but will not rev up -- either in fast idle or in gear. It just bogs down -- it seems the timing changes ...?:(
 
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