Tohatsu M70C warning buzzer

[ajaxcycle]

Hey everybody, I have a Tohatsu M70C that the warning buzzer is coming on and I don't know why. The first time it came on I noticed the tell tale wasn't flowing water and shut it down. I had a friend tow me back to the dock and then once at home I replaced the water pump. The tell tale now flows better than ever - a nice strong stream - and everything seemed good. The first time I took the boat out everything seemed to be fine for a while, then the alarm went off again. I looked back and there was water coming out of the tell tale like ti should. I shut the motor off for a few minutes, then restarted it and it ran fine with no alarm the rest of the day. I am wondering if the thermostat is sticking or if anyone out there has any experience with these motors and has any suggestions as to what may be happening. Thanks in advance.

 

[pvanv]

Re: Tohatsu M70C warning buzzer

See p62 of your owner's manual. You can d/l a copy of your manual at http://www.tohatsu.com/tech_info/manuals.html. Buzzer (and no oil light) indicates an overheat. If the telltale is flowing, the problem could be corrosion in the passages, a stuck thermostat, or a faulty overheat sensor (or the associated wiring).

 

[ajaxcycle]

Re: Tohatsu M70C warning buzzer

Thanks for the input, I have already downloaded the owners manual and was looking for confirmation. You gave me that.

 

[Sea-Rod]

Re: Tohatsu M70C warning buzzer

Make sure you have the correct spak plugs. These motor require resistor plugs otherwse the radio frequency interference from the ignition system can cause spurious alarms and or activation of the speedlimiter. I had this problem when the motor ran at approximately 4500 rpm for more than one minute. After replacing the water pump, thermostat, rebuild kits in carbs, new fuel filters, replaced temp sensor, removing head to check for blockage the problem persisted then I found the plug problem. This seems strange but it is true and it is not all that unusual. If you search the net you will find technical articles on this issue, bad thing is the authorized Tohatsu service center I used was not aware of the issue. Good Luck

 

[TOHATSU GURU]

Re: Tohatsu M70C warning buzzer

Sea Rod,

Can you give me the links to these "technical articles"?

 

[Sea-Rod]

Re: Tohatsu M70C warning buzzer

Look at this article first, it gives a very good explanation of what causes the problem:

members.iinet.net.au/~pauldawson/iame26-spark-plugs.PDF
The name of he article is "Why outboards require special plugs"

The first clue that lead me to this solution was the fact that a universal Faria tachometer requires a 200 mf capacitor to be installed across the terminals to suppress the electromagenetic interference, This is found on the Faria web site and is only required for Tohatsu/Nissan. I have helped two other tohatsu owners with the same problem and had the same results.

 

[TOHATSU GURU]

Re: Tohatsu M70C warning buzzer

What I was concerned about was your statement about activating the rev limiter and/or alarms. The spark plugs cannot cause that problem. The article that you linked to is just an explanation of RFI and some of it's causes. RFI can interfere with a non approved tachometer, however, usually an erratic tach will still be erratic regardless of the plug type. The tach is picking up the signal out of the CD module and aftermarket tachs frequently have difficulty matching the signal wave. Hence the use of a diode to compensate. Unfortunately the use of an extra diode does not always insure that the aftermarket tach will work.

 

[Sea-Rod]

Re: Tohatsu M70C warning buzzer

Note in the article it does say erroneous alarms and or activation of speed limiter funtions could occur and in my case did . My electrical engineering education and years of work with computer systems have taught me that strange things happen when you mix EMI and solidstate systems.
I had to limp 3 miles back to the marina once with the motor restricted to 1500 rpms. I shut off the engine to verify it was not over heating etc then restarted with no problems just to have it reoccur in 5 minutes. So I have to respectfully disagree that it can not happen and is certainly something to check if you are having a similar problem.

 

[pvanv]

Re: Tohatsu M70C warning buzzer

1500 rpm is not ESG engagement. You had a different issue.

 

[TOHATSU GURU]

Re: Tohatsu M70C warning buzzer

And again, it was not a RFI issue. It's that simple. Chances are it was a CDM issue. If you have a twitchy CDM it can be affected by RFI.

 

[weareallnuts]

Re: Tohatsu M70C warning buzzer

Would this issue stop a tach from working?? I rebuilt a Grumman with Tohatsu 70A a few years ago, put in new gauges, the tach worked for a year or so, then started to read sporatically, then not at all. Thanks!
Peter in SC

 

[pvanv]

Re: Tohatsu M70C warning buzzer

That's an alternator tach. Is the motor charging? If the rectifier is partially burnt, that could affect the tach. However, usually, it's a poor wiring connection or a bad meter.