F115TXRB high idle speed

[martinbryner]

I have a Yamaha F115TXRB 4 stroke outboard. This is 2003 year.
The motor will not idle down after startup. Runs at 1200RPM. I have checked all sensors and the Idle air control by swapping with a friends F115. All components check out fine. The problem seems to be with the ECU itself. I have ohmed out all the wires at the ICM to ECU harness and all is OK. The ECU is not telling the Idle control motor to adjust. I was able to get it to slow down by connecting the ICM to the harness on my friends motor while it was running. The motor adjusted closed and I then reinstalled in my motor in that closed position which slowed it down. It will not speed up at restart. You can take the idle air hose off the intake at the ICM and slow the idle down by partially closing the air flow to the ICM.
What happens inside the ECU to cause this lack of responce? Is everything in there solid state? Is there software that can be reloaded?
$1,000.00 is alot to have to sink into this for bad idle speed issue.
Thanks, Marty
I am in the process of trying to find willing person to swap like ECU to confirm my diagnosis.

[99yam40]

read this post and see if it gives any info http://www.yamahaoutboardparts.com/f...e-th15590.html

watch for rodbolt17 to respond to your post and give good advice

[Sparkieboat]

I am sure rodbolt will have an answer..please post your results as I have the exact same motor and will be very interested in your solution.

[rodbolt17]

when you turn the key to off, do you hear the ISC rattle?
the rattle is the ISC resetting in anticipation of the next start cycle.
if it does not either the ISC,wireing or the ECU has issues.
the F115 has more ECU issues than all other yamaha engines combined.

[martinbryner]

Will do. Do you have similar issues?

[martinbryner]

No rattle. I have Ohmed out the wiring harness from idle speed control to ECU. No resistance issues there. It is as if the software in the ECU has just stopped functioning in reguards to Idle speed. I have swapped out every sensor with friends motror and they all work. ECU hookup is different on his since his is later model. Am working on finding another test subject motor that I can put my ECU into to see how it reacts.
Do you know if there is actual software in those black boxes?
Can it be reloaded?
Also, thanks for your help. This can be frustrating facing such an expensive part.

[Sparkieboat]

Rod..I would also like to know if Yamaha has done anything to improve the ECUs for the F115, or will I be buying the exact same defective ECU that came with my 2003 motor if I shuck out $1K for a new one? Is there any other choice besides selling the F115 and getting another motor? If I was to get another motor, what motor would you recommend?? It would have to be a used motor say 2003-2006 or so. I would consider a 2-stroke also. I posted this in Martins thread because this answer should interest him also.

[martinbryner]

Yeah, makes you want to buy brands with overpriced parts.

[rodbolt17]

if the ECU is toast its simply toast.
yes the ECU part number has superceeded a few times.
better? dunno.
typically the ISC starts sticking and the current draw takes out the ECU.

[Sparkieboat]

so if he has to replace his ECU he should also replace his ISC??? and would you recommend replacing the ISC every time you have to replace the ECU?? Is this motor a "keeper"??

[martinbryner]

OK, so the control valve and the ECU will cost me about $1,362.00 including tax.
Let me ask you this. Reguarding sequence of operation. The idle speed control valve opens a little to let more air in and bring up the idle speed when started. Then it slowly closes down some to maintain the idle RPM at around 750 or so. When the motor is placed into gear or when under way, does the idle control valve move around then also, or does it stay at the position where it would maintain a low idle speed? I know you said it reopens after shut off to get ready for high idle at next start sequence.
Now I want to take you for a walk outside the box.
The reason i am asking this is because I may be able to control the idle air control valve by other means.
As I said before, I was able to adjust my idle air control valve by connecting to my friends motors wiring harness. At the position it was in when I disconnected it from his wire harness and reinstalled into my motor, it now idles at around 1000 rpm. I am confident that I can tweak it a little more and get it closed down just right for low speed idle. Then if I need more air at start up, I disengage the throttle from the shifter, give it a little gas and walla, starts right up and I can adjust the idle speed with my throttle. What do you think?
Visualise Ace Ventura fist pumping and pelvic thrusting!

[Sparkieboat]

with my eyes closed..because of the ace ventura thing, I would really like to have some confidence that if i shuck out the money for a new ECU that it will last longer than a few years...I am thinking seriously of just selling my F115 and going back to a 1995 Evinrude 150 looper that I have..actually i have a 1989 merc 150 also..I have strong confidence in them both. I thought I was getting a pretty bullet proof motor with the Yammy..obviously not.

[martinbryner]

Are you having similar issues? I think I have gotten away easy. I have a small idle speed issue that I have a reasonable solution to. This will not effect me in any way. I can start my motor when cold by disengaging the throttle from the gear shift and giving it a little throttle, then turning the key. Bingo. No problem starting. The $350 dollar idle speed control motor is replaced by my manual operation of the throttle plate. It is nice that the $1,000.00 ECU used to do that for me before it crapped out, but I think I can handle it doing it manually with the remote control. It runs fine otherwise. If the ECU continues to crap the bed, I have talked to a third party that said he can reprogram it. This is an option that should be offered by Yamaha. A part that is that essential and costly should be supported by Yamaha in a recycle- refurbish program. If the idle control valve sticks and burns out that function of the ECU, that is what I call poor design. A fuse in that circuit would prevent that from happening. If later versions of the ECU has corrected that issue, then a recall for earlier versions should have been in order. Even if I was offered a chance to head this off at my cost, that is an offer I would have accepted.
I am not trying to start a revolution here. I am just trying to point out why people loose confidence in a particular product or brand. I have owned Yamaha products for over 35 years and have enjoyed many hours of recreation. When other kids made fun of my yamaha dirt bike, I was very loyal and would tell them where to stick it. I am the original owner of this outboard and nobody contacted me to warn me that the idle speed control may stick someday and "F" my $1000.00 ECU in the process. I wonder if this has been recognised and remedied in later versions of the ECU? Why would I want to buy another? I do not mean any disrespect to rodbolt, you obviously know these engines inside and out and have been very helpfull.
When people are on my boat and they see me dealing with the idiosyncrasies of my poorly designed yamaha Engine control unit and Idle control valve, I will tell them that it is a result of an oversite in design that would cost the average Joe about $2,500.00 to get diagnosed and repaired and that I bought into Yamahas reputation and that I was wrong. This same engine had several major componant failures under warranty and I am lucky that those repairs were covered. I did not do anything due lack of maintenance to bring this on. This ticks me off.
Marty

[martinbryner]

For general info. After doing some more research. I have found that yamaha supplied mercury with the 115 fuel injected powerhead for a number of years. If you look at part costs and compare what mercury wants for parts verses what Yamaha wants for what appeares to be the same parts, you can save around 10 percent by buying the mercury parts and putting them on the yamaha motor.

[rodbolt17]

just like almost all EFI 4 stroke machines that use an ISC(IAC) to you autoguys, it needs to be cleaned periodically.
especially if it gets stored a lot.
the ISC controls idle air and RPM based on ground signals from the ECU.
if the ECU trys to change the ISC opening and the ISC is mechanically stuck the over current condition can overheat the circuits in the ECU causing issues.
thats why there is no code for ISC failure.
if its unplugged the ECU may flag a code 37.
if its mechanically stuck the ECU doesnt know it and keeps trying to move it to correct the engine speed.
thats when the problem starts.
happens to ALL brands.
circuits can be tested with a neon ISC(IAC) tester just like the automotive world uses.
diagnostic of that failure should have been less than 30 minutes by a trained shop monkey.
replacement takes about 30 minutes.
at key on two of the 6 wires are 12V, the other four the ECU toggles the ground(current return) to move the stepper motor(pintle) in or out allowing more or less idle air.
this type,speed density EFI has been used at least25 years in the automotive world.
since 2000 I may have seen 6 ECU failures on the F115, failure is rare.