Yamaha F115AET High Idle Issues

[jayw1996]

Yamaha f115 2002 with 350 hours. After taking the boat out of storage for the first time in 3 years, we have done all the servicing from oils and filters etc. We got the boat running and was going well for about 5 hours operation over 2-3 trips, but unfortunately we have now run into some issues. This started with the starter motor blowing so we replaced it straight up, once the new starter was installed we had the issue of the motor starting up but not dropping back to the normal idle speed 600-750 once it had been cranked over it would stay around 2000. After doing all we could from the garage we took it to our local Yamaha dealer to try get it resolved, from there they replaced the Shift Position Switch, Idle Speed Control Valve and a few o rings which did then get the motor idling back to its normal range (and not cheaply). After its first outing the same issue was back and it was idling back up around 2000 and the Idle Speed Control Valve needing replacing again luckily they are replacing it for no extra cost. So now we are stuck, its back at the dealer and they are not to confident on what it could be but are thinking it might be the ecu but thats a big cost for something they aren't confident will resolve the issue. Has this issue happened to anyone else or anyone have any idea what we might be missing here?

Any help would be appreciated!

[TownsendsFJR1300]

I gather they plugged it into YDS (Yamaha computer monitor), did they find any alarms or anomaly's?

[jayw1996]

Yes, tested on the computer but didn’t find anything.

[TownsendsFJR1300]

It'd be nice if they had a similar ECU from another engine to test yours with.

Any idea's Pan, Fairdeal, 99Yam, Roscoe?

[rejesterd]

At idle, it should never get as high as 2000 rpms to begin with. Unless you have a serious linkage problem that your mechanic somehow missed, I would say it's either a damaged throttle plate or a failing ECU that is opening the ISC valve too much. If you cover up the ISC valve inlet with your thumb and the idle doesn't come down to 800 or so, that has to be linkage or a damaged throttle. If it does come down to about 800 when you do that, then I would say your ECU needs to be replaced.

[99yam40]

jay needs to get a copy of the read out to post up.
with Rodbolt not posting any lately, maybe someone can else see something out of whack.

I would be checking timing to see if that is advanced too far.
easy to do with a timing light, but the read out should show what it is sitting at when the idle is too high.

The ECU just sends a request to the ISC, but does not know if it is actually moving.
maybe a bad connection is not allowing the signal to it to actually close back down

when the motor is shut off can the ISC be heard ( rattling) opening back to 100% for the next start up?

[panasonic]

I would like to know exactly what happened to the starter...he said it blew, what does that mean?
Maybe it is just pure coincidence that the problem appeared right after the starter was changed? What was disturbed while changing out the starter...meaning wiring harness...ect.

"This started with the starter motor blowing so we replaced it straight up, once the new starter was installed we had the issue of the motor starting up but not dropping back to the normal idle speed 600-750 "

[pstephens46]

Yes, tested on the computer but didn’t find anything.

How did they determine the parts that needed replacing??? Did the YDS rpm match whatever gauges you have?

[pstephens46]

At idle, it should never get as high as 2000 rpms to begin with. Unless you have a serious linkage problem that your mechanic somehow missed, I would say it's either a damaged throttle plate or a failing ECU that is opening the ISC valve too much. If you cover up the ISC valve inlet with your thumb and the idle doesn't come down to 800 or so, that has to be linkage or a damaged throttle. If it does come down to about 800 when you do that, then I would say your ECU needs to be replaced.

Based on the f50 service manual?

[99yam40]

I too wondered what he meant by the starter blew.
I have never seen a starter blow up before

[TownsendsFJR1300]

I too wondered what he meant by the starter blew.
I have never seen a starter blow up before

I remember someone posting not long ago about a starter "blowing".. Did a search but couldn't find anything.

And agreed, if the issue started when the starter "failed" , perhaps it took out a sensor or ?