Yamaha F250 High Idle Help ........

[Who's your daddy]

I have been having a problem with one of my 2006 Yamaha F250 outboards having a high idle. It idles at 900 RPMs, while my other 2 idle at 600rpms. Also there is a lot of bubles coming from the lower unit of that motor.

Now a little history. I had this same issue a few months ago. Motor ran great except for the high idle. Motors had quit a few hours on them so I took my boat in to get a compression check/leakdown test. Had low compression in 1 cylinder and also had a couple low compression in another motor. Decided to do a complete overhaul on both of these motors, including the high idle motor. When the powerhead was removed, the dry exhaust was checked and it was in great shape, no corrosion, so that ruled out that issue.

After a complete overhaul with new rings, bearings, etc the dang motor still idled high. Took the motor into the Yamaha certified mechanic that rebuilt the motor and he checked the motor out for vacuum leaks, timing issues , etc and found absolutely nothing wrong with the motor. Also checked throttle linkage, all good. Also new thermostats.

What the heck???! Ideas?

[Sequoiha]

The idle is con*****ed by the ECM. From various inputs, could be several things, unregulated air, or a sensor issue, coolant temp maybe, could you provide a download, key on engine off cold engine.

[99yam40]

with 3 motors ,it would seem those readouts could be compared to see what was different.

but needs to be looked over by someone with the proper knowledge

[Sequoiha]

with 3 motors ,it would seem those readouts could be compared to see what was different.

but needs to be looked over by someone with the proper knowledge

Kind of why I asked him to provide the download. So I could look it over.

[pstephens46]

Wonder how many hours? Wonder what the compression tests looked like prior to rebuild?

[rodbolt17]

poor compression wont cause a high idle.
a printout of key on engine off and one at idle should tell why the single electronic throttle system idles about 300 RPM high.
there are roughly 59 codes that the engine can throw.
most will result in a higher than normal idle.

[pstephens46]

[QUOTE=rodbolt17;141819]poor compression wont cause a high idle.
a printout of key on engine off and one at idle should tell why the single electronic throttle system idles about 300 RPM high.
there are roughly 59 codes that the engine can throw.
most will result in a higher than normal

Wasn't my point......just curious why 2 engines needing rebuilding.

[99yam40]

Kind of why I asked him to provide the download. So I could look it over.

Just ment for him to post info from 2 motors

[Who's your daddy]

Thanks everyone...... reason for the rebuild was low compression in a couple cylinders. I charter fish so decided to go ahead and do a rebuild while it was in the shop. Had well over 2000 hours on the 2 motors that were rebuilt. Cylinders We're just honed and re-ringerd, bearings , etc.

[99yam40]

Are you going to post some read outs so someone can help?

[Who's your daddy]

I am in the process of getting the boat into the shop for a download. I removed the intake to look for obvious gasket integrity issues that would cause a vacuum leak,all was good.

[Who's your daddy]

Bought me a Yamaha YDS diagnostic software system. Plugged it in and it showed all normal and no codes. But does show a code history.

[99yam40]

So you know what readings are normal key on motor off and with motor running at idle?

at least look for diferences between the one that runs too low and the others.

posting the read outs should get people that do this for a living to hopefully respond

[Who's your daddy]

No, trying to post up the reading now but it showed file upload failed. I'll keep trying

[Who's your daddy]

Readout one