Stuck in safe mode

[Nuisydney]

Hi there. Recently bought a boat with a Yamaha 40HP 2 stroke outboard.

The sticker for the engine number is missing but I believe the motors a 2003 VETO. I am hoping someone can explain the engine guardian mode and what triggers it as the yellow light is stuck on and the revs are cut to around 2000RPM.

Cleaned out the carbs and found the enrichment solenoid and red switch were both seized so changed them out. Lifted the float sensor in the tank and tested the low oil buzzer with everything checking out on the digital gauge on the dash. Visually inspected both temp sensors and chased wires for breaks or disconnected plugs and everything seems fine. The engine is in brilliant condition with little to no corrosion anywhere.

If anyone can shed some light on this system or can tell me what resistance the float and temp sensors are supposed to run would be a massive help. Cheers

[ausnoelm]

The float "sensor" you are referring to is in the oil tank? if so, it's just a switch, either on or off, the temp sensor is similar, seems like you have an oil issue from your description.

[Nuisydney]

Yea mate the float in the tank. Is there another oil sensor that engages the guardian mode?

[boscoe99]

It is RPM reduction mode. It is not a "safe" mode. Nothing safe about it.

Keep operating the motor with the alarm sounding, or the motor in the RPM reduction mode, and it can be severely damaged. I bring this up only because there are some who think that the motor can continue to be used when it is in RPM reduction mode. They do so at their own peril.

Two things will normally sound the alarm and result in the motor going into the RPM reduction mode. Low oil quantity (float drops) and high temperature (thermoswitch closes).

You mention two temperature sensors. What is the other one?

Do you see a label on the block with some numbers on it? If so, what are those numbers? Look at the CDI please. What are the marking on it?

Where are you seeing a yellow light? On the motor itself or on a Yamaha tachometer or ??? Yellow is normally caution. No alarm. Red is warning. Alarm should sound and motor in RPM reduction mode.

[99yam40]

I do not know about his motor, but on my C40TLRX there are 2 temp switches.
one tells the CDI that the motor has warmed up,
and the other tells when the motor is overheated.

on these autolube motors ,did we discus a level switch inside the screen /tube the float slides up and down on not too long ago?

[Nuisydney]

Yea I pulled her straight out of the water Boscoe99. Thought it was just carb related as I’ve never dealt with a “limp mode” on a small carbureted outboard before.

On the starboard side of the heads there’s two sensors. Both sit in cut outs in the alloy snugged in by their rubber grommet ends. Both are identical in appearance, tried testing resistance on both but I believe they have to be at operating temp before registering anything.

The yellow light is on the engine itself just above the transom bracket facing inwards to the boat. The yellow light is the only one on and there is no buzzer/alarm sounding.

Finding limited information on it but what I have read is there’s 3 lights, a green light signalling everything’s OK. A yellow light signalling engine is in RPM reduction mode. A red light signalling no oil in tank...? All three sit inline on a single small LED light bar.

The only markings on the CID are manufacturers name, Mitsubishi Electric. I’ll get back to you with the engine number mate I’ve lost the paper I wrote it down on.

99yam40 you mentioned one of the sensors tells the CID that the motor has reached operating temperature. Would it make sense to you that the engine might run intentionally in RPM limit mode until the engine has properly warmed up?

[Nuisydney]

The engine number is 1001063

[99yam40]

did someone take a tiller motor and convert it to a remote?

as far as I know the motor warmed up switch just tells the CDI that the motor is warm so the CDI can readjust the timing to normal idle timing after start up

[Nuisydney]

Mate I’m not sure. We bought the boat of an old bloke who mentioned re-powering at some point in the past. Could easily have been a tiller converted to remote but it was never mentioned to us.

[99yam40]

I would think tiller motors were the only ones with lights on them.

with a conversion, who knows what all could be wired up and have problems

[boscoe99]

Looks to be similar to a USA 2003 model 40TLR. Or C40TLR if no oil injection. If no oil injection then of course no low oil warning.

https://www.boats.net/catalog/yamaha...ar/2003/40tlrb

https://www.boats.net/catalog/yamaha...r/2003/c40tlrb

[boscoe99]

Post a photo of the light(s) please.

[99yam40]

well when I looked up #34 pilot light assembly that part show in the H and the R parts breakdown.
I had no idea that was on remote motors

https://www.boats.net/product/yamaha...42b83ce680a208


Boscoe, could it be possible that the strainer is not letting oil in so the float never rises with the oil level in the tank?

if that is true, then the motor is not getting the oil it needs to run

or maybe the float is hanging up and will not rise even if covered in oil

[Nuisydney]

Thanks for the reply boys. I think I’ve found the problem. I’ll go into a bit of depth here in case someone else has this drama.

The three warning lights green, yellow and red are only related to the float sensor in the oil tank. Green - Oil tank is full. Yellow - oil low. Red - oil critically low, revs cut to 2000RPM and alarm sounds. After reading this I knew the problem was elsewhere. The yellow light was stuck on but that shouldn’t cut revs until it’s critically low and no alarm sounding. Still need to sort that issue but I’m thinking a faulty control box.

We launched her last night and she ran absolutely fine for a good 2 hours. Hit some decent chop and immediately triggered the limp mode again.

On this engine there is the CID control box mentioned before with only the manufacturers markings “Mitsubishi Electric” cast into the black plastic. The box is mounted on the Starboard side of the engine and has a switch mounted to the front of it that connects to the throttle linkage through a small “arm” similar to the one that connects multiple carburettors together. All 3 sensors, two temp and one oil float wire into this box.

Did a resistance check on the two temperature sensors on the block when at operating temp. One sensor is for over heat and according to the manual will only trigger after 95 degrees Celsius (makes sense). The second sensor as stated before is to signal the control box when the engine hits operating temperature between 35-50 degrees Celsius. First sensor read 0 resistance inline with the fact that the engine was no where near overheat. The second sensor was all over the place readings from 1-16 ohms then back to nothing.

Looks like a bad sensor and maybe even a weak switch inside the control unit. Working fine until we hit some chop and triggered the limp mode. I was confident we were getting oil to the engine and we were not over heating. I removed the linkage on the control box switch and manually flicked it back into its normal running mode. Monitored it on our way back and all went well.

I am going to chase up a new temp sensor for the 35-50 degree C range and maybe a new control box then re-test. Obviously this system is here to protect the engine so worth having. A friends outboard last month blew when the 2 stroke oil pump failed and didn’t have any warning system in place to let him know.

Might take some time to find parts but will post results here. Thanks again boys

[boscoe99]

Those sensors are just switches. Close with increase in temperature. Called thermoswitches.

Top thermoswitch is for engine warm up. Bottom thermoswitch is for over temperature.

Top thermoswitch is normally open. Closes at 38 ~ 52* C. Bottom thermoswitch is normally open. Closes at 90 ~ 96* C.

Only the bottom thermoswitch closing will cause the alarm to sound.