96 Yamaha 115 2 Stroke Migrating Firing Issues

[tazsman]

Hi Guys,

I have a 1996 Yamaha 115 2 stroke Saltwater Series.
Sorry if this is long winded but I want to make sure I give you guys as any details from past issues and fixes as I can.
I had a sneeze at idle and the boat would stall out quite often. This was an issue since I bought the boat second hand 10 years ago. It was a non problem that progressed.

Last year I changed the fuel pump and fuel filter. I had the carbs cleaned and then I started having a bog/sluggish 3/8ths throttle on acceleration. It would quickly return to full power all the way through WOT. To my dismay, it still sneezed and stalled at low speeds quite often.
I ran the boat and dealt with the problem in the fall and then before winterizing I found two coils were not sparking. Cylinder 1and 3. The top 2 cylinders. With a winter storm approaching I couldnt start working on it untill this spring.

This spring I changed out the spark plugs and cleaned the spark plug wire connections and now #3 Coil was firing just fine. okay great.

I checked and there was no change in engine sound on cylinder # 1. So cylinder one is not firing. I changed Coil # 1 and it started sparking.

fyi. I do not have a compression tester yet. I am also using ngk br8hs10.

I checked spark plugs by switching them around and the same Cylinder #1 was not firing.

I picked up some tips from another thread and re-cleaned my top carberator and I checked the fuel hose and on the tank side of the bulb and it looked a bit deteriorated at the connection. I sheered off a bit of the hose and reconnected it. I think it may have had a small air leak. the bulb feels really firm now.
I also changed the water seperator to a more shallow sized one.

Question 1: Is it ok to change to the smaller size?

So before my most recent carb cleaning, cylinder 1 was not firing. I reassembled the carb 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.

Question 2 and 3: So, what happened? How did the issue migrate to cylinder 2?

Has to be spark plugs! I pull #1 and #2 plugs and they are fouled up. The plugs are new and I only ran the boat a few times this year.

Question 4 and 5: Am I running too rich? Is it a timing issue? I backed out the pilots 5/8 of a turn. The maual recommended 3/8-7/8.

Anyhow, I switched the plugs from the lower cylinder to the top cylinder and they both are firing now. However, the idle sound difference on the port side cylinders 1 and 2 was much less than the change in sound of the starboard side cylinders.

I just picked up new plugs and i will water test this week.

Can anyone help explain my questions. Should I do anything else before my water test?

Thanks in advance

 

[99yam40]

Re: 96 Yamaha 115 2 Stroke Migrating Firing Issues

It is best to test things properly to see if they are in spec like the service manual states.
Just pulling a plug wire off while running can cause the spark to just jump anywhere it can and sometimes that can be internal to the coil or cause a problem back in the CDI causing a cap to go bad.
If fuel lines are going bad replace them and all filters. If you clean the carbs and do not replace/clean fuel lines and pump could mean just dumping trash back into the carbs when fired back up. make sure the tank is clean also.

compression, spark, and timing are all easy to test
the fuel/air ratio to each cylinder is a lot harder to prove, but spraying a fuel/oil mix into each carb throat while running will tell you if a cylinder is running lean

 

[PPCS]

Re: 96 Yamaha 115 2 Stroke Migrating Firing Issues

My engine (1999 115 2s) had the same issue as you're having as discussed in my topic. This is how I fixed similar problems to yours.

1. Check compression is equal on all 4 cylinders
2. Check spark on all cylinders (with special tool or just by pulling plugleads and keeping them close to the plugs. You can see the spark jumping from the lead to the plug.
3. Take off fuel filter and inspect for clogging
4. Take off all carbs and have them cleaned and redone by a specialist. You have to disassemble the carbs and clean all the small canals. Then the specialist has to set all the pilots etc correctly in teh carbs. I had this done by a professional.
5. Synchronize the carbs and done you are.

We found a piece of dirt in the carbs which was restricting the fuel flow to one cylinder. Note that only when we took the carbs off the second time we found the piece of dirt. You can check wheter the carbs are the issue by pulling off the air filter and blocking the air going in to one carb at a time. When the engine starts to run better for 1 or 2 second, when blocking the air going into that carb, you might have found the issue.

Good luck

 

[tazsman]

Re: 96 Yamaha 115 2 Stroke Migrating Firing Issues

Tested the boat in the water today after replacing the plugs. One thing i noticed was that the fuel bulb did not get hard or feel like it was pushing gas through it when pumped? Regardless, she started right up and idled at 800-900rpm without a cough or stall. I hit the throttle and had full power out of the hole and onto plane. I brought it back down to a troll and she ran at 600rpms without a hiccup. Powered up again to wot at 5400rpms and the engine ran smooth as could be.

Can anyone chime in on why the bulb didn't get hard or feel like it was pushing fuel but the engine ran fine?

 

[tazsman]

Re: 96 Yamaha 115 2 Stroke Migrating Firing Issues

I have another question. I read the J. Reeves Carb adjustments and I also read the manual in regard to setting the carbs. Do I need to readjust the carbs on the water like J Reeves recommended or should I stay Low Speed Settings as the manual recommended. i noticed that the engine I have had a smaller adjustment compared to 95% of the other yamahas low speed setting.

The manual said to turn out the low Speed needle to 3/8 to 7/8. The engine feels like it is running better than it has for a long time. Do I make any further adjustment?

"PPCS
the fuel/air ratio to each cylinder is a lot harder to prove, but spraying a fuel/oil mix into each carb throat while running will tell you if a cylinder is running lean"

PPCS- How should the engine respond if it is running lean and I spray the mixture into the throat?

I pushed the auto choke while it was running and it immediatley shut down the engine.