2004 Yamaha F90TLRC will not shut off

[NWwalleye]

Hello,
Got a question for someone smarter than me ...
Here is what is happening ..

My engine starts fine and runs great..
It will shut off and start every time with the key and kill switch when engine is cold ...
But, after it has warmed up to operating temps.. It will not shut off with the key or kill switch.
I have looked at all the connections and wiring. Do not see anything out of the ordinary ..
Maybe CDI ??
I don't know anymore ..
Any and all help would be greatly appreciated ..
Thanks ...

[99yam40]

I have read of motors with hot glowing carbon in the cylinders causing a motor to keep running without spark from spark plugs.

You can always check with a spark tester or timing light while problem is there to see if spark is still going or not.

Then do a decarbon if needed

[rodbolt17]

the F90TLRC was carbed.
the F90TLRD was EFI.
are you sure yours is carbed?

[NWwalleye]

Mine is a F90TLRC ..
It is carbed ..

Any ideas ???

[rodbolt17]

carefully test the ground path from the engine block to the key switch.
carefully test the circuit path from the black wire at the keyswitch(switch off) to the white wire at the engine ECU connector.
may help if you add a 3 or 4 amp load to the circuits, circuits MUST be disconnected to add a load.

[NWwalleye]

Ok.. I will give it a try soon..

Could it just be the CDI / ECU ?
Yamaha rep/mech here seems to think so ..

Thanks for your help ..

[rodbolt17]

I have seen more harness/connector failures than ALL Yamaha ECU failures since 2000.

you really really want a stupidly simple test?

[NWwalleye]

Ok.. I will test it today ...

But, why only when the engine is hot ?
Why not all the time ?

[rodbolt17]

Ill play your silly ****. why?

for starters if your mechanic refers to a CDI on that motor go find a real tech.
the F90 NEVER used CDI.
TCI.
HUGE difference in operation and operational theory.

that stupidly simple test that common sense combined with the fact I am lazy as heck?

simply straighten a paper clip.
work it into the ECU connector white wire making sure the clip has a good contact.
tape the clip so it cant back out.

now when it fails to shut down simply use a jumper lead and take the clip to a known good ground.

if it dies go chase the harness/keyswitch.
if it doesn't CAREFULLY inspect the ecu connector and pin.
if the connector and pin are good its the ECU.

its up to you to insure the ECU ground path is intact.

its a stupidly simple Transistor Controled Ignition, hence TCI.
does NOT use stator output voltage for ANY function of ign except battery charging.

at key on the ECU applies 12V to the ign coil primary.
the ECU, based on pulser coil signals, shut off the transistors to interrupt the current flow creating secondary spark.
its a waste spark.
means both coil leads spark at the same time everytime.

that transistor is an electronic equivalent of a set of points and has been used by various manufactures since at least the late sixties.

but try that stupidly simple test, saves a bit of time.
like I say I am rather lazy.

[NWwalleye]

Sorry for using the wrong terminology ..

Thanks for helping me ..

It was a great FIRST experience on a forum were people of less expertise are here to ask for help..

When I can find the time.....
I will use your stupid simple test and post results .

[NWwalleye]

Ok.. Did the test ....
.
Jumping the white wire to a ground on the block.. made the motor die !!!
Now I think we have the problem figured out ...
Thanks again ..

Now ..one more question...
Instead of chasing or stripping the wiring harness ...
Could I just run a new White wire from the key to the ECU ?

[boscoe99]

[QUOTE=NWwalleye;

Now ..one more question...
Instead of chasing or stripping the wiring harness ...
Could I just run a new White wire from the key to the ECU ?[/QUOTE]

You could. But do you want to? And what if that did not solve the problem?

Maybe the white wire in the engine harness is good and it is just a connectivity issue at the ten pin harness coupler.

Maybe the white wire in the ten pin harness is good and it is just a connectivity issue in the ground wire to the key switch/kill switch.

Find the problem. Fix it and only it.

[NWwalleye]

Makes sense ..
Thanks ...

[rodbolt17]

dunno why buuut.
seems every time there is an issue folks immediately jump on the "its a computer" train.

folks in the last 20 years I may have seen 8 computers fail on Yamaha Volvo and mercrusier.

may have seen 5 coil failures on the above.

I have a 24 Albemarle with an EFI Volvo 5.7 at the shop.
they now own a spare 1100 dollar mefi 4 unit.

some heavy equipment mechanic has maintained and trouble shot it to death.

you would not take your lear jet to the ford dealer.
you would not take your lexus to a briggs and Stratton dealer.
why would you take your boat to someone with NO training on your equipment?

[boscoe99]

[QUOTE=rodbolt17;9253

you would not take your lear jet to the ford dealer.
you would not take your lexus to a briggs and Stratton dealer.
why would you take your boat to someone with NO training on your equipment?[/QUOTE]

I agree with your take it to someone that has the tools and knowhow. But, how is a boat owner to know who that may be?

Some Yam master techs should not have gotten their diplomas.

Some Yam dealer mechanics don't seem to know much more than Joe Backyardigan.

Boats and motors sit at a dealer all too long. Expensive repair bills. Problem may not be solved.

Customers piss money into the wind. Yam pisses money into the wind paying for warranty repairs, and extra labor, for dealer tech misdiagnosis.

Pity the poor tech at a Yam dealer who has not been to school or who has not completed all the courses. The Yam SM is so deficient that even if he wanted to he could not learn on his own about all of the different models and how they operate. He likes marine work but gets frustrated, says screw this, and goes into a different field.

Being a boat owner can be a lot of work. More than most might want to do. Thank goodness for the overall reliability of todays motors.