M40D2 guardian mode?

M40D2_NZ

Recruit
Joined
Dec 11, 2018
Messages
4
My M40D2 (branded as Mercury Lightening XR) enters guardian/safe mode after a impact with short/sharp chop or coming off the back of a wave when at wide open throttle (or close to). Coming to rest and turning off the engine and waiting 10 seconds will fix the problem.

I have replaced/had the following work done in the last few weeks:

new fuel lines/bulb
water pump & thermostat
new spark plugs and boots
new fuel filter
carbs cleaned and tuned

The owners manual states that the low speed electronic safety governor will kick in when it detects low oil levels and keeps the RPM below 2300, even if the throttle is wide open. There is plenty of oil in the engine.

I am wondering if a faulty sensor unit or wiring connection could be causing the issue.

How could I check on the water?

Thanks for your time!
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,500
Is there a low-oil or over-RPM or over-heat warning lamp/buzzer? Any loose or shorted sensor wires? I would verify operation of the overheat sensor and the oil level sensor. When you jump off a wave, everything slams, and the RPM could go over max. A semi-shorted sensor wire could trigger an alarm such as low oil or overheat.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
What's the situation on flat calm water cond while running wot, has same issue ?

Happy Boating
 

M40D2_NZ

Recruit
Joined
Dec 11, 2018
Messages
4
Is there a low-oil or over-RPM or over-heat warning lamp/buzzer? Any loose or shorted sensor wires? I would verify operation of the overheat sensor and the oil level sensor. When you jump off a wave, everything slams, and the RPM could go over max. A semi-shorted sensor wire could trigger an alarm such as low oil or overheat.

Thanks for the replies folks, I am going to start tracking down/checking the wires this week.

If the high speed ESG is limiting the RPM do I just go slower? (shock horror!), I don't feel like I am riding the boat THAT hard.
 

TOHATSU GURU

Admiral
Joined
Jul 22, 2004
Messages
6,164
It sounds like you were bumping up against the rev limiter...Is this on a cat inflatable? If so you need to understand that the propeller needs to be in the water not in the air. Wave jumping with an engine that has a rev limiter will be an issue. Other than that...Think in terms of pulling out the service manual and running the electrical checks on the CD Module.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Which type of boat is that 40 HP powering ?
Is it a manual or electric trim 40 HP- OB ?
Is currently being used in fresh or salt water ?
How old/new is that 40 ? With few or huge hours of use ?
How loaded were when encountering such problems ?
Was the combo running parallel to water level along neutral trim or other trim settings at wot when that happened ?

How about OB/transom height. Tohatsu OB's loves to run while lower leg skims skims right under upper plate at plane, once there OB will achieve top prop thrust in all water cond, except when water is too windy, wavy in which case will need to throttle much less or prop will aerate/ventilate badly.

If all wiring is found Ok, heat sensor and thermostat needs to be diagnosed properly if working inside Tohatsu's tech specs, for that will need to count with a Service Manual or change both for new ones..

If all mentioned points are found OK, probably OB counts with a prop that triggers the rev limiter too fast in which case will need a higher pitch same diam prop to decrease wot revs as usually loaded and forget all about inviting the rev limiter to the water party. LOL!!

Happy Boating
 

M40D2_NZ

Recruit
Joined
Dec 11, 2018
Messages
4
Which type of boat is that 40 HP powering ? Fryan 440 - small ali dingy.
Is it a manual or electric trim 40 HP- OB ? - electric tilt
Is currently being used in fresh or salt water ? - salt
How old/new is that 40 ? With few or huge hours of use ? - 2007, 180 hours.
How loaded were when encountering such problems ? - just myself on the boat.
Was the combo running parallel to water level along neutral trim or other trim settings at wot when that happened ? i will check tomorow

How about OB/transom height. Tohatsu OB's loves to run while lower leg skims skims right under upper plate at plane, once there OB will achieve top prop thrust in all water cond, except when water is too windy, wavy in which case will need to throttle much less or prop will aerate/ventilate badly.

If all wiring is found Ok, heat sensor and thermostat needs to be diagnosed properly if working inside Tohatsu's tech specs, for that will need to count with a Service Manual or change both for new ones..

If all mentioned points are found OK, probably OB counts with a prop that triggers the rev limiter too fast in which case will need a higher pitch same diam prop to decrease wot revs as usually loaded and forget all about inviting the rev limiter to the water party. LOL!!

Happy Boating

Thanks Sea Rider - I have replied inline to your questions

I am still learning about all this, but what your saying is that with a little more trim up it might come right? I can take some photos of how it is setup tonight.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
M40D,

So it's a dingy. Is it a Sib or Rib version, tiller or with central console and remote ?

Meantime would recommend to download the Tohatsu M40D Owner's Manual:

https://www.tohatsu.com/common/owner..._OM2018_EX.pdf

Page 54 (Trim Angle) have a look at the correct trim angle position, deck weight distribution when boat is on plane whether counting with electric or manual trim.

But those drawing examples won't work spot on if OB has a transom height mismatch that will need to be water determined by a visual inspection check when combo is under way..

Happy Boating
 
Last edited:

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
M40D2,

Is this 440 Fryan same exact as yours, it's a tinnie...

Click image for larger version  Name:	Fryan 440.JPG Views:	1 Size:	101.7 KB ID:	10687753

Happy Boating
 
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