UPDATE: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

[PPCS]

Hi Guys,

Went out for skiing this saturday and had a wonderfull day until my engine started to let me down. Suddenly the engine started to run rough on low rpm between 1100 and 1900. It does vibrate a little more and I think it is missing one cylinder at that rmp range. Above 2000rpm the cylinder starts to join the pack and the middle and top end power did not change and works like it used to. I also noticed that the engine sometimes caughs and dies when I put it in idle and it runs at a lower rpm at idle.

My guess is that there is a fuel or spark problem at low rpm's and that at higher rpm's it starts to work again. The engine does not rattle or make strange noises. It just vibrates a lot more at the 1100-2000rpm range and indicates that is is running on 3 cylinders from idle to 2000rpm.

You guys have any ideas? I brought the boat to my mechanic and hopefully he will have some time this week, but he was not sure he could make it. Hopefully you guys can help my diagnosing the problem as far as this is possible with this limited info. I just hope that this is an easy fix. My meachanic was not shure what the problem is and hoped that there was someting wrong with the fuel/carb delevery on one cylinder.
Can you guys determine some things that might cause the problem?

Thanks in advance for helping me out!

Peter

 

[Bob Gilvary]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

I'm going with your mechanic on the fuel at idle having a problem, but it all needs checked before jumping in on it. Fuel, spark, and compression.

Fuel/water separator?

 

[PPCS]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

I'm going with your mechanic on the fuel at idle having a problem, but it all needs checked before jumping in on it. Fuel, spark, and compression.

Fuel/water separator?

Thanks for helping me out! The fuel/water separator was also the first thing my mechanic mentioned, how is this linked to the above described issues??

Any more ideas??

Thanks,

Peter

 

[PPCS]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

OK, compression on all the cylinders is very good and equal. So I can rule any damage to the block out. Furthermore my mechanic said that all the sparkplug sparked, so whats next do you think??

Regards

 

[kenneth80]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

check fuel pump diaphragm. squeeze the bulb and pay attention to the fuel pump. if you notice any gas coming out from it you either buy a fuel pump kit and rebuild it yourself or you buy a new pump. new pump is only 35-40 dlrs.. next would be a complete rebuild of the carburators. soak them,clean them and blow with compressed air.

 

[PPCS]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Thanks Kenneth! You mentioned the squeeze bulb, do you know whether it has to stay firm after squeezing when the engine is off. I noticed the other day that when I squeeze the bulb until it is firm, a few seconds later it is not as firm as it should be (when the engine is turned off). Does this sound normal to you?

Also I'm wondering how a bad fuelpump / diagram can cause the engine to run on 3 cylinders, because this goes for al four right??

Thanks again for helping me out. I just wish I had more technical knowledge........

 

[tazsman]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

I have the same issues with my 96 115 Saltwater Series Yamaha. Last year it was coughing/sneezing at idle and sometimes while going <2000rpms to the extent it would stall out. I figured it was a carb issue and brought it to a mechanic for rebuilding. The guy who worked on my engine was a yamaha tech and said the carb was really filthy and carbonized etc. I ran the boat and the sneezing was still an occurance but not as often. The kicker is I now lost power durning acceleration for a few moments then it took off. WOT- ran great! I adjusted the carb to enrich the mixture by 1/8 to 1/4 turns and there was no change in the sneezing or acceleration.

I was also having intermittent problems with the fuel bulband keeping the prime. I figured it was a fuel pump so I replaced it. the bulb is now okaybut No Other Change.
Replaced the water seperator. No Change.
Fuel filter-No Change.

I checked the spark plugs, replaced them, and tested the spark. There was no spark from coil cylinder 1. I replaced the coil and it sparked but the engine did not miss a beat when I pulled the plug wire.?? Just ran the boat with the new coil. Again, No Change with sneezing or acceleration.

Whats next? Any advice is appreciated.

 

[PPCS]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Your problem sounds a bit worse than mine, but I might have some clues for you. My Yammie mechanic said that if there is a problem with the ignition and it is not the coils, the problem can be caused by faulty magnet(input ignition) on the flywheel, or worse the CDI computer. Do you know for sure that there is a solid spark in all cylinders??

If you have I might think there is still something with the fuel delivery. Hopefully this will help you, because I am unfortunately no mechanic..........

Questions for you:
- Why change fuel/water seperator? What are the sign of a faulty one?

Good luck!

 

[tazsman]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

I am definitly getting strong spark to all cylinders.

I changed the water seperator because it is the cheapest fix to start with.

Moreover, when I heard the coughing I thought that it may be water in the gas stalling it out. Same thing with the loss of power on acceleration. If water worked its way in I thought it would result in the loss of power while under load. If the water seperator becomes overwhelmed, water will make it into the engine.

 

[tazsman]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

I forgot to add, I had a similar loss of power but much worse in the past. I couldnt' get the boat on plane and it hardly ran in neutral. I changed out the seperator and it ran perfect.

In my case, my boat sat for a long time this winter and Spring so i may indeed have a lot of water condensation in the tank. I will go and replace the filter before my next trip and get back to you.

 

[PPCS]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

OK more news,

Today I went out with the boat to isolate the problem any further. I now know for sure which cylinder it is, because I pulled the plug leads one by one untill the enige did not respond to the removal of the pluglead. Now I know which cylinder is the culprit. Next I changed the plugs, coil en plugwire with another cylinder. But the same cylinder still is not running.
You can hear a spark when holding the pluglead next to the plug, so it is definitely sparking.

So My mechanic pulled the carbs off and he will clean them over asap. But on first inspection the carbs were clean! Hopefully the carb is the problem....

What do you guts think of it? Is it carb related, or is there still something with the ignition somehow??

Thanks!!

 

[tazsman]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Okay, so you are in the same boat as me. haha.

Which cylinder has no change in the way the motor runs? Mine is cylinder 1.

I think it could be the fuel line with the primer bulb causing the issue. This is what my gut tells me. Seems like there is a flow problem at the point where the engine needs a quick injection of fuel. This is at the initial acceleration point. This was my thinking when i changed the fuel pump too.

why do you think it is ignition?

 

[PPCS]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

First of all I still HOPE/PRAY it is the carb!!!!!!!! Because my mechanic is cleaning it as we speak. I don't think it is the fuel line or primer bulb, because when pumping the primer bulb there is no change. The cylinder is still not running. I don't know the cylinder number, but if you look back from the console to the engine it is the lower left cylinder.

If it is not the carbs, the problem can only be ignition related. My second guess is that the spark is just not strong enough the spark the plug and thus the fuel mixture.
At higher rpm the cylinder starts to join the pack, so that is where the ignition has the strenght to make a good spark.

Hopefully some experts over here can help me figuring out what the problem is, because it is driving me CRAZY.......

Regards

 

[99yam40]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

as was said before, test things to see what is going on.
If you do not have the proper test equipment then buy them and the Yamaha service manual for your motor that explains what to do or take it to someone that has them and the knowledge to use them. It does not sound like your mechanic is someone that is up on Yamaha and has not tested voltages or anything else from what you have said so far

 

[PPCS]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Hi Guys,

Thanks for the advice. My mechanic has all the testing equipment, but leans to my opinion too much to trial and error methods. That's why I asked you guys to think with mee. Yesterday I went to check out my boat/engine and I've got NEWS. As said before we pulled the carbs of and cleaned them. When reinstalling the third cylinder was still not fully joining the pack. When restricting the carb of the third cylinder it started to run and run very well. This was a sign that there still wass something wrong with the carb of cyl 3. So we pulled them off again and this time we cleaned them very very thorougly and found some piece of dirt clogging one off the canals in the carb of the third cyl. This was GREAT news.

So we installed the carbs again and cracked on with synchronising them and making the fine ajustments. Unfortunately the plastic piece connecting the throttle to the carbs broke. This &%$#@ simple piece of plastic.......... Yamaha doesn't have the piece in stock, so it is now on backorder. I said BACKORDER.................... for this stupid piece of plastic, which can ruin my season. So I went to a large Yamaha dealership and asked for that part. Luckily they had a few old salvage engine's, so they pulled the piece right off for me and I had the stupid part!!! So I raced back to my boat and installed the plastic piece. I started the engine, and it runs like a charm. But I didn't had the chance to fully test the boat, because it was late and my boat was blocked in by other boats. Tuesday I'm going to fully test the boat, but I'm confident that we found the problem. When pulling the plug of the 3rd cylinder the engine starts to run rough again. This change proves that the third is running again.

I will keep you guys posted on how the testdrive went! I'm very exited and keeping my fingers crossed untill tuesday!

Regards,

Peter

By the way, here are some pictures of my boat/engine. What do yo think???

 

[tazsman]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

That's great news. I was reading the manual and it is pointing to a fuel blockage in the lines or the carb. Is 3 cylinder on the starboard side? I am guessing that it was the starboard side and that coincides with the carb that was clogged? both starboard?

So mine is cylinder 1, so it should be the Port Carb? Can anyone confirm this?

If you have any pointers or if you have any advice for me before i clean mine, please share.

I am glad you found the issue. I have to find the time to pull and clean mine.

Thats a nice looking boat. What is the make, year?

Thanks for the help and response.

 

[99yam40]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Nice and clean boat you have there.

How is that rope rub rail attached

 

[PPCS]

UPDATE: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Hi Guys,

Thanks for the compliments!

Concerning the engine there is good and bad news! The good news is that at low rpm the engine runs silky smooth and on all 4 cylinders. It has never run as smooth as this! So my original problem has been solved!

The bad news is that above 3000rpm the engine starts to vibrate and run very rough. There is also no power and the holeshot is gone. When pushing the throttle real hard it will eventually reach 4500rpm and that's it. This however was perfect when I put the boat in............

So we solved the running on 3 cylinders on low rpm, but we created another problem at high rpm.
I think that there is somekind of problem with the fuel delivery of the carbs, as this is the only thing that has been changed, because the carbs came off twice What do you guys think??? It is driving me crazyyyyyyyyyyyyy.


@ Tazsman, If you take off the airfilter, you can see the 4 carbs. The upper ones are the closest cylinders to the carbs and the lower ones are the cylinders furthest of the carbs. Left is left and right is right indeed! Hopefully this will help ya. Take of the carbs and clean all the small needles and canals thoroughly. My low rpm problem has been solved that way. Unfortunately the high RPM prob is new and I don't know what it is...........

 

[PPCS]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Update: Went for a testdrive yesterday and the engine is perfect now! It turned out to be some kind of dirt in the carbs blocking the fuel to one cylinder. So now I'm gonna enjoy my boat today.

Thanks for all the great help and if you guys have any questions please ask!!

Regards,

Peter

 

[tazsman]

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

Re: Yamaha 115 2-stroke (1999) running on 3 cylinders at low rpm

That's good news.

I checked the fuel hose on the tank side of the bulb and it looked a bit deteriorated at the connection. I sheered off a bit and reconnected it. I think it may have had a small air leak.

I also changed the water seperator to a more shallow sized one. Is it ok to change to the smaller size?

I moved on to the top carb for a cleaning. If you remember, cylinder 1 was not firing. I found a bit of debris inside a canal located by the pilot. I saw it shoot out into the chamber by the flaps when I sprayed it.
I put it back together and fired her up. I pulled the cylinder 1 plug and there was a slight change in engine idle. So sounds like it fired. Moving on, I pulled the wire on the one below, I believe it is Cylinder #2. Correct me if I am wrong. There was no change in engine idle/sound. So, what happened? How did the issue migrate to cylinder 2?
Has to be spark plugs! I pull em and they are fouled up. They are new and I only ran the boat a few times this year. Am I running too rich? Is this a result of the one cylinder not firing at the 3/8ths throttle?

Anyhow, I switch the plugs from the lower cylinder to the top cylinder and they both are firing now. Also, when I pulled the plugs the idle sound difference on the port side cylinders 1 and 3 was much less than the change in sound of the starbrd side cylinders. Does this sound like Sh*tty plugs? Fouled plugs? Do you think its plugs at all?

thanks