2011 optimax 175 hp Speeds up in idle by itself

**stan73** · 12-13-2018, 08:06 PM

Hi
Hope someone can steer me where to start on this
When slowing down and going into neutral the engine speeds up to 2400 rpm.
Making it difficult to dock and water skiing even worse...The only thing that resets it
is shutting the engine off and restarting it/. It does not do this all the time. It's a
crap shoot and scares the heck out of you when it happens

**Scream And Fly** · 12-14-2018, 01:36 AM

I may have the service manual for this. Have you tried disconnecting the battery? If the problem is cured temporarily after restarting the engine, it might be the ECU, but I think others here will have more suggestions. If you can, disconnect the battery fora half-hour and reconnect it to see what happens.

Greg

**stan73** · 12-14-2018, 03:34 AM

Originally Posted by Scream And Fly

I may have the service manual for this. Have you tried disconnecting the battery? If the problem is cured temporarily after restarting the engine, it might be the ECU, but I think others here will have more suggestions. If you can, disconnect the battery fora half-hour and reconnect it to see what happens.

Greg

Yes I tried that, it's also been doing this for 2 seasons. I thought it might be the idle trim on the smart guauges
but that did not lead me anywhere. Once it idles up, an action where you go to neutral, it stays at high rev
only once did it back down on it's own...Another item it "seems" worse if I am just idling around, go into neutral and it speeds up. Always key off and back on it resets, to a normal idle...

**XstreamVking** · 12-14-2018, 03:52 AM

If it were the tps etc it should sound an alarm. Most sensors being out of range sound a beep code. I would guess it is caused by the fuel pressure diaphram system on the fuel rail where it is sending too much fuel to the engine. This would not signal an alarm. It is controlled by the fuel pump which you are cycling off and on with the key. Fix it before running it anymore as this could be a dangerous situation.

**Scream And Fly** · 12-14-2018, 08:23 AM

@stan73 check your private messages.

**stan73** · 12-14-2018, 10:39 AM

Do they sell those diaphragms yet or are they still saying the US EPA won't let them?

**XstreamVking** · 12-14-2018, 10:52 AM

yep, dealer or online....

**stan73** · 12-14-2018, 10:56 AM

There are 3 fuel / 2 air and other one 3 ,? forget what they call it, which one do you think would cause this problem?

**XstreamVking** · 12-14-2018, 12:02 PM

I believe the fuel pressure one since it leaks extra fuel into the system. Air press works on air injectors. Tracker balances the air and fuel. I had a fuel press dia go bad on my 225 opti and it had a run away idle. Torn fuel diaphram and I just replaced them all. You may have a sticky spring or a bad diaphram.....A code scan would be a good idea before tearing into it. But, it should be beeping or a sensor fault showing on your smartcraft(if you have one).

**stan73** · 12-14-2018, 12:16 PM

Ok will try and find them, no beeps, smart craft gauge shows nothing, have to wait till summer, Thanks for the direction on this
cheers Stan

**Motv18** · 12-15-2018, 12:44 AM

You can bleed test for leeks with a fuel gauge

koeo a cupple times should see 30-40 on rail 20-30 on vst and then I should drop to atmosphere 10-20 on rail. if it holds 10+ psi for more then a minute no leaks. If it stays over 20 theirs pressure on the air side or regulator stuck.

It actually sound like your gauge is getting stuck in ski/tow. Pull the connector and run around for bit if it doesn’t do it it’s the gauge or neutral switch.

Ive bumped my troll befor and was confused as f’ why it was hitting 1k when I shifted to fwd.

**stan73** · 12-15-2018, 12:54 AM

My problem is it does not do it often. Hard to pin point it.
getting stuck in ski/tow. (what does that mean?)
Pull the connector (Which connector does it have a name?
it’s the gauge (which gauge?)

Thank for the help

**flabum1017** · 12-15-2018, 08:47 AM

TPS can still be faulty, it will only throw a code when it's out of range. it can still be faulty and be in range and not throw a code. You will need a scan tool and look at the TPS in live data while throttling it up and down slowly looking for it to jump around down near idle. Engine does not need to be running to check it.

**stan73** · 12-15-2018, 12:03 PM

Thanks I will look at that too

**Motv18** · 12-16-2018, 10:28 PM

Made an assumption when you said smart gauge.

The tach and speed have cruse control modes that controls the throttle. Troll for 1000 rpm or less trolling. And ski/tow that controls full rpm launch and drops to a set rpm. So you can drive not work the throttle.

If if you have those they can make it do weird things

if if it’s a merc monitor it won’t have those modes. So ignore me.