Frustrating F225 High Idle

[bravajo2]

Folks;

I stumbled across this forum and I was hoping that someone could offer some advice on my 2004 F225 with 350 hours. Here is my problem and the information that I gathered:

Boat has been idling 900-1100 rpm when in neutral for a couple of weeks. Initially it was intermittent but now it is very consistent. If I turn the motor on/off it occasionally returns to a normal idle but not consistently. I put the motor on the YDS to diagnose the ISC, TPS, etc. Here is what I found:

All throttle linkage recalls were performed on this motor.

1) With the motor off (key in on position), cool and in neutral and using YDS engine monitor the TPS voltage and throttle valve opening seem to fluctuate a little between 0.9 and 1.1 degrees (.735-.742 V). I think the spec for the TPS is slighly lower than what the monitor shows. Nobody is touching the throttle for it to fluctuate. This fluctuation bounces the TPS voltage around a fair amount and it seems to happen at throttle positions other than idle.
2) I performed the stationary test of the ISC and could clearly hear the clicking noise of the ISC valve.
3) With the engine running at idle the ECM seems to have the ISC set at 80% (I've been told this is too high). I tried the active tests with the engine running and when the test moves the ISC to 100% the idles picks up and when it closes the ISC to 67% the idle speed reduces. At least I know the ISC is doing something.

In speaking with knowledgeable people I have been told that the TPS should have a rock solid reading and the fact that it is fluctuating could lead the ECM to do something strange to try to compensate for the constantly changing TPS reading. Is this a problem?

If that is the case then is there any way to assure that the fluctuation is a faulty TPS and not wiring related or possibly related to the incoming 5v power supply?

Appreciate any guidance. I have full YDS dumps if that helps.

Thanks,
Joe.

[99yam40]

I am no expert , but I think you should make sure the 5 v reference voltage is steady and not being drawn down lower than it should be for some reason.

Too bad Rodbolt17 has not been posting hear lately as he would have the answer for you.
You might search for and read some of his posts to see if you can get any info out of them.
If nothing else helps find a shop with a Yamaha master tech that works there

Outboard training - Master Technician

[boats.net]

Probably need to start with sync and link, if haven't synced throttle linkage and throttle body's then need to do so.

[bravajo2]

Last time I linked and synced was about 2 seasons ago.

How often do I need to do that?

Would that explain the bouncing TPS reading?

thanks,
Joe.

[seahorse5]

If a sensor is out of spec, you will get a 900 rpm idle.

There were 2 Coast Guard recalls for sticking throttles on the Yamahas from the 2002's on up to a certain serial number. Check with a dealer to see if both were done if your motor was in the affected recall group.

TPS voltage at idle is .695-.705 measured between the pink and black wires.

[Sim_08511]

You will have to replace the TPS and this should sought it out. Seen this a few times, as soon as the TPS starts fluctuating that's it. It should be a constant voltage at idle.

[Sim_08511]

Oh yeah also if it was the input voltage to the TPS you would have issues through the whole rev range

[bravajo2]

Thanks Sim. I have been hearing that a fluctuating TPS could be a problem.

Did you see the same result (high idle) in previous cases?

Seahorse,

Motor had all throttle linkage recalls done previously.

Thanks again,
Joe.

[Sim_08511]

Yeah will cause a high idle, also can make the motor fluctuate at low revs.

[bravajo2]

Thanks. I'll let you know how it works out.