2012 115 Yam issues

Hello all. I am fairly new to this forum and would like to throw a question out to see if anyone has had the same problem. I have twin 115 Yams on my 2012 2360 Wac. The motor had 65 hrs on them when I got the boat and the issue was there then. My issue is this: My port motor kicks at certain RPM's usually 4000 or higher. The funny thing is that it does not happen all of the time. I can get it to WOT and keep it there for sometimes 1/2 a day then suddenly it starts to buck until I lower the RPM's down to 4000. It has gone on for a year now and I have chased it in many directions. I notice that sometimes my gauge on the dash will read 13.5-7 volts and the other motor always reads 14.4-6. The port motor, however, reads 14.4-6 volts as well at times seemingly with nothing wrong. I have been told it was a fuel problem and a dirty VST filter or injectors.
Here is what I have done so far:
1. Batteries
I have put a third battery and designated it to the house battery and now each motor also has a battery. I have also switched the batteries as well from motor to motor. Taken them out and had them inspected for charge and all good. I do have a VSR in the boat as well.

2. Filters
I have changed all of the filters on the boat and motors including cleaning the VST filter in the port motor.

3. Change of components from one motor to another
I have switched the wires, coils and plugs from motor to motor.

4. Injectors
I have taken out and cleaned the injectors from the port motor.

5. I have put a computer on it and no codes have shown up. (At idle speed)

When I bought the boat I noticed that the previous owner had taken the 3rd battery out and left me with a ground lead which lead me to believe he may have changed the wires around in the VSR. I do have a wire in the setup that I am not sure should be there. I have seen a few schematics on this particular setup and never seen this wire setup. Could it be a power issue causing this??

I have spent a lot of time on the net to solve this issue as well as looking up schematics for the VSR and now I am posting on here for some assistance. I would appreciate any feedback one can share.
Regards
John

jnobby said:

Hello all. I am fairly new to this forum and would like to throw a question out to see if anyone has had the same problem. I have twin 115 Yams on my 2012 2360 Wac. The motor had 65 hrs on them when I got the boat and the issue was there then. My issue is this: My port motor kicks at certain RPM's usually 4000 or higher. The funny thing is that it does not happen all of the time. I can get it to WOT and keep it there for sometimes 1/2 a day then suddenly it starts to buck until I lower the RPM's down to 4000. It has gone on for a year now and I have chased it in many directions. I notice that sometimes my gauge on the dash will read 13.5-7 volts and the other motor always reads 14.4-6. The port motor, however, reads 14.4-6 volts as well at times seemingly with nothing wrong. I have been told it was a fuel problem and a dirty VST filter or injectors.
Here is what I have done so far:
1. Batteries
I have put a third battery and designated it to the house battery and now each motor also has a battery. I have also switched the batteries as well from motor to motor. Taken them out and had them inspected for charge and all good. I do have a VSR in the boat as well.

2. Filters
I have changed all of the filters on the boat and motors including cleaning the VST filter in the port motor.

3. Change of components from one motor to another
I have switched the wires, coils and plugs from motor to motor.

4. Injectors
I have taken out and cleaned the injectors from the port motor.

5. I have put a computer on it and no codes have shown up. (At idle speed)

When I bought the boat I noticed that the previous owner had taken the 3rd battery out and left me with a ground lead which lead me to believe he may have changed the wires around in the VSR. I do have a wire in the setup that I am not sure should be there. I have seen a few schematics on this particular setup and never seen this wire setup. Could it be a power issue causing this??

I have spent a lot of time on the net to solve this issue as well as looking up schematics for the VSR and now I am posting on here for some assistance. I would appreciate any feedback one can share.
Regards
John

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Anyone with some ideas?

Have you or the prior owner been running ethanol blended fuel? Before I do anything with a randomly rough running engine that's been subjected to ethanol blended fuel and perhaps stored for a while I give it a heavy dose of Seafoam and keep on runng it to see if it fixes itself. Ethanol blended fuel is absolute worst thing to ever hit us boaters. I absolutely never, ever use it anymore and am more than happy to pay whatever it costs for non-ethanol gasoline... Been in and out of my outboard enough times fixing clogged this and thats from that enthanol gumming.

deepsea21 said:

Have you or the prior owner been running ethanol blended fuel? Before I do anything with a randomly rough running engine that's been subjected to ethanol blended fuel and perhaps stored for a while I give it a heavy dose of Seafoam and keep on runng it to see if it fixes itself. Ethanol blended fuel is absolute worst thing to ever hit us boaters. I absolutely never, ever use it anymore and am more than happy to pay whatever it costs for non-ethanol gasoline... Been in and out of my outboard enough times fixing clogged this and thats from that enthanol gumming.

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Thanks for the reply deepsea21. I have changed all the filters including cleaning the vst in this one motor and not the other but it continues to give me the same issues. The other runs like a top all the time this is the weird thing about it.

jnobby said:

Thanks for the reply deepsea21. I have changed all the filters including cleaning the vst in this one motor and not the other but it continues to give me the same issues. The other runs like a top all the time this is the weird thing about it.

Click to expand...

Ahh yes that wonderful VST filter burried deep inside the VST tank burried deep inside the engine (I'd love to get my hands around the neck of the Yamaha engineer who placed that tank and filter so deep inside the engine!)

Are there separate fuel tanks or are both engines fed by one tank? I am wondering if it could be a fuel flow issue in which flow becomes insufficient at higher RPM's with both engines running and the fuel really being sucked from the tank(s). Regardless of whether or not you have twin tanks or a single fuel tank, get to the tank(s) and look for the fuel pick-up line that runs down inside the fuel tank and sits at the bottom. Pull the pick-up line and see if the manufacturer placed a little filter on the end of the pick-up line(s). Some manufacturers do and they NEVER EVER SHOULD as that is the last place anyone would think to look for a filter. As the engines run and suck fuel, particulate that could have been left in the tank since maufacture can begin to get stuck on that little filter... As you keep running, they keep sucking fuel and more gets stuck on it to the point it restricts flow... Then, you throttle back or shut down, fuel sloshes around in the tank and those particles drop off that little filter and start floating around again. Everything runs fine until it happens again they get again get stuck on that stupid little filter. There is absolutely no need for a filter on the end of the fuel pick-up line if you are running an in-line fuel-water seperator filter, and even if you aren't, no need for it as each engine has it's own fuel filter in the rear under the cowling. I had a friend who chased a ghost for months until someone told him about the possibiliity a stupid $2 filter could have been stuck on the end of that pick-up line. Sure enough, there was, and he got rid of it and his problem was solved.

With regard to the voltage readings you are getting, they seem fine.

I think the voltage issues is the problem. 12.4-14.7 is quite a dramatic change. Its fluctuations worry me. I change the Rectifier from one motor to the next and it did not change at the gauges. When I changed the ECU, however, the problem went from the Port gauge to the Star. gauge. I need to take it for a test run to see if it is the ecu. Has anyone had problems with their ecu on their F115??

jnobby said:

I think the voltage issues is the problem. 12.4-14.7 is quite a dramatic change. Its fluctuations worry me. I change the Rectifier from one motor to the next and it did not change at the gauges. When I changed the ECU, however, the problem went from the Port gauge to the Star. gauge. I need to take it for a test run to see if it is the ecu. Has anyone had problems with their ecu on their F115??

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No probs with the ECU on my 2002 Yamaha F115 with about 600 hrs on it. Voltage is a little over 12V cold and holds at 13.5 volts from idle to 6000RPM. But, now that sounds like you've found when the ECU is swapped the voltage issue you see moves with it. Would be interested to hear if the running problem moves with it as well as your experience is something new to me.

Well, the change of the ECU did NOT help my issue. Back to the drawing board and start all over again. Pulled the VST apart and checked the filter again and cleaned it so it was totally see through. Well, it actually did not take too much cleaning as it was pretty clean already. Still think it is a voltage problem as the gauge consistently moves. The Yam dealers here are grasping at straws as well. Had the injectors professionally cleaned new seals as well. Have not had it for a run since I cleaned the VST filter tonight. Thanks for all of the responses. deepsea21...I called the boat company and they said there is a filter on the end of the hose so will check out that as well.

jnobby said:

Well, the change of the ECU did NOT help my issue. Back to the drawing board and start all over again. Pulled the VST apart and checked the filter again and cleaned it so it was totally see through. Well, it actually did not take too much cleaning as it was pretty clean already. Still think it is a voltage problem as the gauge consistently moves. The Yam dealers here are grasping at straws as well. Had the injectors professionally cleaned new seals as well. Have not had it for a run since I cleaned the VST filter tonight. Thanks for all of the responses. deepsea21...I called the boat company and they said there is a filter on the end of the hose so will check out that as well.

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AHHHHH... so there is a filter on the fuel pick-up line! Don't just check it - GET RID OF IT and see what happens. It an seem clean and clear until it gets clogged with debris in the tank again while running. Let the other larger filters deal with any debris in the tank.

I am thinking that if there is a restriction anywhere in a common fuel line it could cause one of the engines to kick even if they are both on the same fuel system - maybe the fuel line when it splits to each engine one line is a shorter run than the other - maybe one engine develops a bit more fuel suction than the other so a common restriction in the fuel line could cause a problem to show up in only one engine when they are both really trying to suck fuel.

Each line has its own pick-up and F/W separator therefore totally independent of one another. I checked the check valve and it is just fine blew on it both ways and it did what it was suppose to do. Spring works well. Going to take it for a burn tonight perhaps.

jnobby said:

Each line has its own pick-up and F/W separator therefore totally independent of one another. I checked the check valve and it is just fine blew on it both ways and it did what it was suppose to do. Spring works well. Going to take it for a burn tonight perhaps.

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If there's a filter on that fuel pick-up line and you have separate tanks / separate F/W filters I'd pull or cut that filter off the pick-up line. It can seem clean an clear but remember what I said in the beginning - As the engines run and suck fuel, particulate that could have been left in the tank since maufacture can begin to get stuck on that little filter... As you keep running, they keep sucking fuel and more gets stuck on it to the point it restricts flow... Then, you throttle back or shut down, fuel sloshes around in the tank and those particles drop off that little filter and start floating around again. Everything runs fine until it happens again they get again get stuck on that stupid little filter.

Just to be certain - I'm talking about a tiny filter that could have been placed on the end of the fuel pick-up line that sits down in the bottom of the fuel tank... It's the 1st filter fuel may have to pass through before it ever gets to any fuel lines, F/W filters, the fuel bulb or to the engine

Yes, this is what I checked the other day. Check valve is operating perfectly. I blew into the hose and it seemed very free from obstruction. Remember that this pickup line is right beside the other and I have no problem with that other engine.

jnobby said:

Yes, this is what I checked the other day. Check valve is operating perfectly. I blew into the hose and it seemed very free from obstruction. Remember that this pickup line is right beside the other and I have no problem with that other engine.

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Understood. If both fuel pick-up lines are coming from the same tank that doesnt' seem like it would be the problem then. At least you know it's not the ECU after swapping that.

Here's an idea - try swapping the coils between the engines. Coils have a way of performing fine when they are cold but as the get hot under an outboard engine cowling (just like inside an engine compartment of a car) their ability to build serious voltage to fire plugs can deteriorate as they age. They'll fire fine until you get to high RPM's and they get hot under the hood. When hot and at high RPM they have to be able to take and build a sufficient charge to create spark 6x as fast as at idle. If a coil is going bad, it can't build enough charge fast enough at high RPM when it gets hot - it can cause random misfires due to no spark until you decrease RPM and the coil again has more time to accept/build a charge between firings... For what it's worth at this point! Keep me posted.