2003 Yamaha 50 hp 2 stroke problem

[Toddboat]

After winter storage, my 2003 Yamaha 50hp 2 stroke outboard was running awful, and stalling in idle. I cleaned the carbs and plugs and it ran well for 10 minutes or so, then returned to hesitating and eventually stalling and not restarting.
The last time I tried it, it ran for a couple minutes, then stalled and would not restart. I suspected the engine was flooded, so I tried the next day and I was able to start it, run it for a couple minutes and then it stalled and would not restart.
I believe the engine may be flooding and fouling the plugs. I know that if my diagnosis is correct, I will have to make sure that the needle and seat are sealing properly to stop the engine from flooding, otherwise the plugs will continue to foul over and over again. My question is this... if my motor will start and run for a couple minutes, then not restart, then start up the next day and run for a couple minutes, then not restart, then start up the next day, etc, etc... have I properly diagnosed this as a flooding condition, or are there any other problems that could produce this same behavior?
Thanks!

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

100 views but no replies. This post deserves a bump!

 

[T_Herrod]

Re: 2003 Yamaha 50 hp 2 stroke problem

What did you put in the gas for storage? How old is the gas.

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

I didn't put anything in the gas, which I know is a mistake for winter storage. The gas is from last summer (12 months old) Do you think that alone could be enough to cause these symptoms? Today I ran it on muffs and had the same results. I changed the plugs and it ran smoother, but still stalled out after less than a minute.
I'll try new gas (89 this time) and see what happens. Do you add anything to the gas all the time, or just for winter storage? Thanks!

 

[99yam40]

Re: 2003 Yamaha 50 hp 2 stroke problem

do not just put in new gas, drain and flush tank, lines, and carbs.
sounds like you do not run it often, so I would recommend adding stablizer to fresh fuel every time you add to tank

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

Thanks, I'll empty all the old gas out of the carbs, filter, gas lines, racor, and tank and refill with fresh fuel with recommended amount of stabilizer. You're right, I don't run it too often. Maybe 20 times a season (when it's working right!)
I'm going to run it off of a separate tank at first, so I can mix it with 50:1 TCW-3. There is about an inch of air in the oil hose, and I want to make sure that goes away before relying solely on the oil injection system to provide oil.
Thanks again!

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

Today I drained all old gas out of the entire system, even drained the carb bowls. I tried to start it at that point and it would not start (proof there was no leftover gas in the motor). Then I pumped fresh 93 octane gas into the motor from a separate tank and started the motor. It started right up, but I had the same symptoms as before. It would run for 20 to 30 seconds then stall. So I know the problem is not stale gas. Next I plan to do the following...
-new battery
-carb rebuild kit and cleaning
-new fuel pump
At that point, if nothing works, then I'm off to the mechanic. It could be some odd electrical leak or something that I would never be able to track down myself.
I do have two questions about the theory behind how an outboard works that would help me troubleshoot...
1.) Once a motor is started, does the health of the battery at that point make any difference to how it runs?
Once started, couldn't the battery be disconnected for that matter, and still the motor would keep running?
2.) If I prime the bulb and start the motor and it runs for 20 to 30 seconds and then stalls, could that really have anything to do with the fuel pump? Isn't there enough fuel in the carb bowls to make the motor run for at least a minute or so without relying on the fuel pump? Or does the fuel pump maintain a certain level of fuel in the carbs at all times such that if that fuel level drops a small bit, the motor would stall out?

Thank you for any insight you may have into these two questions. Sometimes I stumble on the theory which prevents me from understanding how to best attempt a fix for problems.

 

[T_Herrod]

Re: 2003 Yamaha 50 hp 2 stroke problem

A new battery is probably a waste of money. I would agree with the carb work and fuel pump work. Did the gas have a funny smell? Bad gas smells like varnish and can cause the needle to stick and can plug the small passages in the carb. I have the same engine in my boat so i will be watching this thread very close.

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

The gas didn't smell bad. I actually put it in my car and the car runs fine. I'll skip the battery and move on to the carb rebuild and fuel pump. Today I ran the motor on the fresh 93 octane gas but did not add any oil because I wanted to give the motor the best shot at running properly with the right viscosity for the fuel for it to atomize correctly.
Now that I see that the new fuel didn't make a difference, I'm going to try again later today with oil in the fuel.
There is a one inch gap of air in my oil line, which I think is pretty normal after winter storage. I'm running the motor on muffs in neutral, so the motor is not calling for oil from it's inboard tank. I know that some people will not agree, but I believe that without oil, a motor loses compression and can stall because of that. The oil is what seals the tiny gap between the rings and the cylinder from the little I know about the inner workings of the engine. The cylinder has grooves in it so the oil stays on it.
Later today I'll give it a good run with a 50:1 mix of fresh 93 octane and TCW-3 oil to see if I have any better results.
I should note that the problem with stalling that I have is only in idle. The motor seems like it would run forever at higher RPM's. I haven't had the "no starting" problem since I've only been starting it here and there, not repeatedly like I was when I was stuck on the water. In other words, I'm not flooding it anymore, but I think flooding may still be a problem. When I primed the bulb today, I filled the carb bowls for sure, but the bulb never got hard. I think a float or two may be stuck open, hence the carb rebuild as soon as I can get the rebuild kit.
Hoping for better luck later today with the cylinders well coated with TCW-3.

 

[T_Herrod]

Re: 2003 Yamaha 50 hp 2 stroke problem

I'm running the motor on muffs in neutral, so the motor is not calling for oil from it's inboard tank.

I may be wrong but don't 2 stroke engines need oil anytime they are running.

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

You may be right, but the arm that triggers the oil pump is connected (via the carbs) to the throttle linkage on the carbs. So I don't believe the motor gets oil when in neutral, but I could be wrong. The reason I don't think it does is that I have an air gap in the oil line that stays unchanged when I run the motor in neutral. I could have a faulty oil pump, I suppose, but it's always worked in the past and I've heard they are very reliable, so I don't think it's malfunctioning. I think Yamaha probably knows that the motor can do without oil in neutral because people don't run them for too long (or too high RPM's) in neutral for too long. Yamaha recommends starting the motor after storage with a 50:1 mix until all the air gaps have left the oil lines, so I know I can add the oil to the motor at least while I'm testing it.

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

Update...
Today I drained all the gas out of the lines, the filter and the carbs and added TCW3 to the fresh 93 octane gas.
I ran the motor to work the oil into the cylinders. Unfortunately, I had the same symptoms as before. The motor runs strong above idle speed, but stalls very quickly when it drops to idle speed.
I am moving on to my next several attempts at a fix... fuel pump and carb rebuild, and will keep this post up to date as I track down the problem. I hope I find that there is a real broken part somewhere, because if this problem is just a matter of fine tuning some knob or something, my approach will have been an expensive one :facepalm:

 

[99yam40]

Re: 2003 Yamaha 50 hp 2 stroke problem

the oil link adjusts how much oil is injected, but it never stops it completely.
Higher RPMs need more oil than low RPMs.

Sounds like you just need to clean carbs.

Take carbs apart and clean well, make sure to follow link and sync procedures in service manual after putting back together
They have o rings instead of gaskets and should be able to reuse them if not damaged.
Kits have lot of stuff you normally do not need. If you find something you need after taking apart then order it

You can take apart and inspect fuel pump , replace parts if needed or buy new pump

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

99Yam40, I've been reading a lot about carbs and how they work. Last time I took them apart, I removed all the screws thinking I was doing a very thorough cleaning job, not realizing that I may have been changing settings by doing so. The idle mixture screws, for example, I removed them and when I reinstalled them I tightened them all the way. Not sure I was supposed to do this. Would a link and sync procedure address this setting? Can you tell me briefly what a lync and sync procedure is, and if it's something that a DIY'er can attempt with no past experience? I'm going to assume this is a carb issue until it's fixed or until I've completely ruled out the carbs. Thanks for all of your input!

 

[99yam40]

Re: 2003 Yamaha 50 hp 2 stroke problem

http://forums.iboats.com/yamaha-suz...sync-procedure-need-clarification-366637.html

see if this will help you understand it some.

But you need to get a Yamaha service manual for your motor if you plan on working on it yourself.

Pilot screws are to adjust the idle mixture into carbs and should be run in lightly seated and then backed out to the specs in manual

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

Thanks, I'll read through the post in your link... looks pretty involved at first glance. Looking for a PDF version of the manual that hopefully I can download so I don't have to wait for 15 day shipping (typically from Canada from what I've seen on eBay). I don't have the tools (like the tach) to do this job myself, but if they aren't crazy expensive, I'll be upgrading my toolbox to include any that I'll need. If I don't get the motor running right within the next couple weeks, I'm going to take it to the shop. If it were October, I'd tinker with it all winter until I fix it myself, but being that it's the start of the season, I don't want to be without a boat now. I guess I need a second boat... one to fulfill my boating hobby and one to fulfill my tinkering hobby!

 

[Toddboat]

Update

Update

Update...
I got a new battery, which just as someone suggested, did nothing to change the way the motor ran.
I needed one anyway considering I opened the last one to add distilled water to it before realizing it was a sealed battery that was not supposed to be opened... oops. :facepalm:
I downloaded the service manual for free and read through it. I don't have the link right now, but if anyone is interested, I will find it again and post it here. I cleaned out the carbs again and did my best to link and sync them. I can get the motor to run in idle by simply increasing the idle speed by adjusting the idle screw.
Unfortunately, the motor still ran rough and coughed every so often and had intermittent hesitation. Still not happy with the outcome, I did the following...
I removed all fuel from the filter, carb bowls and lines. I added 6 ounces of Seafoam to my external tank which has the fresh 93 octane gas in it and ran the motor on it for about 15 minutes. While running, I removed the spark plugs one at a time to see if any particular cylinder was giving me the problem. Removing the top or bottom plug made no difference, but removing the middle one helped marginally. It wasn't enough of an improvement to suspect anything is terribly wrong with the middle cylinder. Once the motor had heated up, I figured there was no harm in doing another compression test. I got exactly 105psi in all cylinders. So I believe the motor is very healthy, and that the problem may not be fuel related.
While tinkering with the motor, I found that I would get a mild shock from the throttle control when I touched the metal part of its handle while turning the key. This leak may explain why my battery dies pretty quickly when left attached.
So now i'm thinking that my problem may be electrical. Partly because I've done everything I know how to do on the fuel side, and partly because the problems I have never fall into the "simple fix" category. :cold:
So tomorrow I'm going to bring the boat to the mechanic and find out what's really going on. If it were winter, I'd tinker with it until the spring, but I don't want to spend my whole summer with the boat stuck in the driveway given how short the season is.
I'll provide an update when I find out what the problem was.

 

[Toddboat]

Re: Update

Re: Update

So I brought the boat in to the mechanic only to find out that he cannot get to it for a week or more anyway. I described the symptoms to him and he said, as others have, that it sure sounds fuel related. He recommended removing all plastic and rubber parts from the carbs and letting them bathe in carb cleaner for a couple days. I'm doing that now, although it'll take 6 days because I only wanted to buy enough carb cleaner to submerge one carb at a time ($42 just for that).
I've got one carb bathed and now reassembled, the second carb is in the bath now.
I noticed there was a lot of debris in the bottom of the bath after I removed the first carb. I was surprised considering I thought I had cleaned it thoroughly the first time. This time while disassembling the carbs, I noticed two things that I hadn't noticed the first time around. First, there is a small hole that connects the main (hi speed) jet to the intermediate (low speed) jet. This time I cleaned it out good by spraying carb cleaner into the main jet while holding a finger over the other end of it, thus forcing the carb cleaner through the little hole and into the low speed jet. I think this hole may have been clogged on one or more of the carbs, but it's hard to tell. They aren't clogged now.
Second, I noticed a gasket (o-ring) that was ripped and part of it was missing. I bought a new one for $6 and replaced it.
It is located between the carb and the intake manifold. I may be wrong, but I believe that if part of this gasket is missing, it may allow air into the cylinder, thus creating a lean condition. This was on the middle cylinder, the one that sounded a little off. Tomorrow I am going to remove the manifold to see if the missing part of that gasket may have gotten sucked into the crankshaft case. It is not outside (near the reed plates), so I doubt it is in the motor. My guess is that someone tore it when cleaning the carbs and never replaced it with a new one.
If I do get the boat running after reassembling the carbs, I will not know if the fix was due to my manual cleaning of the small hole between the jets, or from the carb bath, or from the new gasket. Or perhaps my efforts will not fix anything, in which case it's back the mechanic I go.
I'll keep everyone posted, I know this is riveting.

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

Finally got everything back together again. Tomorrow morning I'll test it on muffs. Couldn't find the other half of the broken o-ring in the crankcase. When I removed the reed valves, I realized they were a little sticky with oil, so I cleaned them off. Must be a common thing considering the oil gets injected in front of them and then gets sucked through them. I guess the pressure generated by the moving pistons is more than enough to overcome a sticky reed valve.
If it doesn't work tomorrow, then it's very unlikely to be a fuel side problem. At this point, I've basically rebuilt/cleaned the whole fuel side of the motor. Haven't taken the fuel pump apart yet, but it's easy to troubleshoot by priming the bulb, which thusfar has done nothing to solve the problem.
If it doesn't work, I guess next I'll be learning a lot about the electrical side.
I have spark in all 3 cylinders, but it does look a bit weak. Granted the sparks I saw were just while turning the motor over with the starter, so I'm sure they were not the strongest sparks the plugs can generate.

 

[Toddboat]

Re: 2003 Yamaha 50 hp 2 stroke problem

No luck today. Top carb needle valve wasn't sealing, so the engine flooded. I fixed the needle valve and got the top carb to seal off and hold fuel without flooding the motor. Still, the motor would not start. It's possible I didn't wait long enough to allow the gas to evaporate before trying again. There was a good amount of white smoke leaving the prop after my attempt to start it. I don't want to keep starting it because I have a leaky oil seal at the prop which at this point may have let all of the LU oil leak out. I'm going to replace the seal and refill the LU before trying to start it again so that I don't so any damage to the gearcase.
When I removed the bad seal, I found that there was only one oil seal at the prop, even though the manual calls for two.
Whoever worked on the boat last must have felt that they could get away with just one seal. By doing so, it allows a lot of room for the one seal to pop out of its housing.
I will keep this post updated. I find that it provides a history of events very beneficial to myself, even if not so beneficial to others. I think it's a good idea to keep a log like this any time you do a repair.