2003 Yamaha 115 HP 4 Stroke EFI Starting Problem

[JDPMN55125]

A friend has:
115 HP 4 Stroke EFI
Model F115TLRB
Serial Number 68VL101495

After the boat is cruising on plane and brought abruptly to idle, the motor will die.
The motor runs perfectly at idle and all RPM ranges while on plane.
Then it will not start until after a cool down period of at least 15 minutes (time can vary).

He brought in for service. I was with him. He explained the entire scenario.
The dealer replaced both fuel filters, spark plugs, oil.
Of course the motor started after this work was performed.

However, once on the water the same problem persists.
He has discovered that he can start the motor by pushing in the button on the remote control,
raising the engine speed and turning the ignition key.
The engine will die if the engine speed is reduced and the shifter is in neutral in a normal manner.
However, if he very quickly lowers the engine speed and shifts into neutral and into forward the engine will continue running.

What should his next steps be?
What is likely the problem?

[TownsendsFJR1300]

What is his neutral, warm idle RPM running at?

Checking the parts diagram I don't see a fuel cooler : https://www.boats.net/catalog/yamaha.../2003/f115tlrb but it likely has one.

Fuel goes thru one end and out the other. Another line pumps sea water adjacent(same unit) in and then out of the unit cooling the fuel, I would check the unit for any clogs.

If that's clear, when was the last time it was "linked and synced"?

[fairdeal]

an odd set of symptoms IMO - if accurately described.
hard re-start due to flooding, clearly.
But how does that match with "brought abruptly to idle, the motor will die"

FWIW it has the familiar fuel cooler

[rejesterd]

Hello.

Typically the reason an engine has trouble starting again (after it's been running for a while) is because fuel vapors have formed. These are sent back through the air intake to be burned. But if too much vapor is sent, then you have trouble starting it because the air/fuel mixture is too rich. That's probably why when he opens the throttle while in neutral, it can start again.. opening the throttle gives an extra shot of air, which evens out the mixture. Later models have a solenoid valve that temporarily stops vapors from going back into the air intake. I don't know if your model has that, so someone with experience on this model might know how best to address this issue.

As for the stalling, that could be improper linkage or an air leak. If you fast-idle it and cover the ISC valve intake with your finger (assuming you can reach it), you can spray some starting fluid around the air intake to see if the idle speed jumps/changes. If it does, you have a leak and the gasket(s) will need to be replaced.

Get the service manual, as it will give you detailed steps on how to adjust the linkage. It will also give you ideas on what else the problem might be in the troubleshooting chapter. Worth the $90 or so.

[JDPMN55125]

To my knowledge the motor has never been "linked and synced" since he purchased the motor in 2003.
Idle speed, I do not know right now. Seems to be normal, when shifting into gear there is no loud clunking.
Will check the fuel cooler for clogging.

Thanks very much for the replies!

[pstephens46]

To my knowledge the motor has never been "linked and synced" since he purchased the motor in 2003.
Idle speed, I do not know right now. Seems to be normal, when shifting into gear there is no loud clunking.
Will check the fuel cooler for clogging.

Thanks very much for the replies!

Need to know the idle speed. May be too low. I assume the mechanic did NOT hook up the laptop and use the diagnostic software. Usually get a more accurate rpm measure that way as well as many other parameters.

[TownsendsFJR1300]

Need to know the idle speed. May be too low. I assume the mechanic did NOT hook up the laptop and use the diagnostic software. Usually get a more accurate rpm measure that way as well as many other parameters.

Yep, I was trying to get the idle speed as well.

Op, PLEASE POST THIS. "Normal" means nothing..



My F150 was too low but stalled under different circumstances. Yamaha REPLACED the entire TB assembly UNDER WARRANTY (which wasn't needed-inept mechanic).

I eventually found a MT that synced the idle correctly (years ago-with lap top, etc) and it's still 700 at idle..
A little correct knowledge goes a LONG WAY..


*From Op's first post:
Quote": However, if he very quickly lowers the engine speed and shifts into neutral and into forward the engine will continue running." End quote.

Fairdeal (or anyone else), would / could (if even installed), the shifter cut off switch (if bad) in the engine cause this issue?

[fairdeal]

If the idle speed were to be "too low" - what would be the fix?

[TownsendsFJR1300]

If the idle speed were to be "too low" - what would be the fix?

My F150, (probably the same as your engine), the low idle was adjusted (I believe, it's been at least 10 years), with the TPS, shutter adjustment, syncing on TB's, manometer)(and possibly some other adjustments). He did this with the engine running , hooked up to the lap top, etc.

My factory idle (common issue back, 2006, 2007) was about 600, in gear, lower...

RB (who has / had the same engine) posted a how to fix(his F150 did the same).



Lemme see if I can find it.. Found it:

Specifically posts 18 & 21: http://www.yamahaoutboardparts.com/f...-problem/page2

[pstephens46]

Wasn’t there an issue with chafing of the ISC wiring in some of those models? Who knows? Guess many are not used to quick responses on forums and give it a few days before returning.

[JDPMN55125]

I spoke with the onwer this evening.
He confirmed I accurately stated the symptoms.
I don't believe the mechanic used Yamaha diagnostic equipment to check the engine when last serviced.

What are the thoughts about the "shifter cutoff switch" being faulty as mentioned by TownsendsFJR1300?

If I can access the boat tomorrow (it is my friend's boat, motor and not at my house) I will get the idle speed and post it.

Thanks for the repsonses thus far!

[pstephens46]

I spoke with the onwer this evening.
He confirmed I accurately stated the symptoms.
I don't believe the mechanic used Yamaha diagnostic equipment to check the engine when last serviced.

What are the thoughts about the "shifter cutoff switch" being faulty as mentioned by TownsendsFJR1300?

If I can access the boat tomorrow (it is my friend's boat, motor and not at my house) I will get the idle speed and post it.

Thanks for the repsonses thus far!

See if your friend will join this forum to answer directly. Save time and aggravation.

[JDPMN55125]

See if your friend will join this forum to answer directly. Save time and aggravation.

He has no internet, computer or cell phone.
I apologize for the aggravation.

[JDPMN55125]

I checked the idle speed today wiuth the tach in the boat.
The tach is not digital.
Initial idle speed (cold start) was 900 rpms.
After a few minutes idle speed was 700 rpms.

[rejesterd]

The warmed-up idle speed might be ok, but that doesn't tell you if the link/sync is ok. You have to look to see if all the throttle plates are moving together in-sync. Best to get the service manual and go through that procedure step-by-step. Maybe one plate is not closing fully and it's letting fuel vapors in when it shouldn't (making it hard to restart when warm) and letting too much air in when slowing back to idle (causing it to stall).