Yanmar warning beeper chirping

Hi all

Just recently the warning alarm on my 1984 raw water cooled Yanmar 2GM20 has started chirping at low revs and the overheat light is also flashing in sync while the alarm is chirping

I don't think that the engine is overheating is this can happen not to long after start up when the engine is still cold

There is plenty of water flow out of the exhaust at low revs and when it happens if I increase the revs it will stop

I have googled it and there are other cases of it happening and some say it is a fault with the panel

Any thoughts would be appreciated

Regards Don

Just googled this Donk
I've had an o"day 30 with this same engine for over 20 years.
first, yanmar only offered this particular engine in the raw water cooled version. i had at one time had this same problem. here's what i found. at the rear of the engine there are a couple of openings in the block and the head that allow the cooling water to circulate through the block and head. there is a housing like piece that the sending unit is screwed into on the rear of the head. here's what happens. since its raw water cooled rust builds up in the water passage between the block and the head thereby reducing the flow and creating a hot spot thus tripping the alarm. this can become a major problem. with this hot spot it can become hot enough to crack the rear most valve seat. if it does you are **** out of luck as it can't be repaired and its a new head time. temporarily here's how to fix the problem. remove the housing that holds the sensor. (two bolts) then get a very stiff wire such as a 1/8" welding rod, bend the end with a 90deg elbow that is about 2 or 3 inches long. then start poking in a downward direction opening up the passage way. i will say that this isn't an easy thing to do, since you have to get in some real contortionist ways to access it. you will also need a good light to be able to see. you will not see any reduction in water flow out the exhaust since the water is flowing as normal in the rest of the engine. this problem will be a recurring issue with this engine in the raw water configuration. i solved this issue when i rebuilt my engine by installing the aftermarket freshwater cooling system. unfortunately this won't be an easy thing to do since sen-dur no longer manufactures it for this engine, but they might have one that can be adapted.
this is a good engine except for the fact that they usually don't wear out, but destroy themselves internally from rust and corrosion. another issue with this cooling system is that the water passages in the exhaust manifold become clogged with rust and corrosion. thus destroying it. then you really are ****ed. yanmar no longer sells the manifold. i don't think that the manifold for the 2GM will crossover fit.
i would remove the exhaust manifold and get it cleaned out. i boiled mine out with radiator cleaner and did a lot of poking to get it cleaned out.
this is on of the big headaches of a raw water cooled engine that has been out of production since 1980 or 81

Well my 3GM used to do this exact thing but it was just a low charge alarm which was why it went off when I raised the revs slightly. I did absolutely nothing to fix it (beyond raising the revs slightly when it did it) and it never gave me any actual problems.
.

Hi to all

Had a bit of a look at this problem again today

Put a multimeter across both batteries and there is over 14 volts at fast idle so i dont think it is a charging problem

Removed the temp sender wire from the sender and it was still chirping so i dont believe it is temp related

The problem appears to have got worse and the waterproof light (the one that indicates water between the upper and lower saildrive diaphrams ) is flashing in conjunction with the chirping but it is a shaft drive not a saildrive

The chirping will be there from idle to 2000 rpm and increases in frequency with revs but at over 2000 rpm it stops

Looking at all of the above i believe there is probably a panel fault that is causing the chirping not a mechanical fault with the engine

Any thoughts

Regards Don

I have just looked at a wiring diagram on the net and it appears that the tachometer sensor and the saildrive sensor share a common earth so perhaps there is a bad earth and it is earthing through the saildrive circuit instead

Any auto elects on here that might confirm this

Regards Don

Not sure what earth circuit ?
It is very simple.
Main switch supply PLUS to all devices.
If any sensor goes off.... Grounds individual globe.
The same apply for buzzer.
Buzzer works independently on any globe.
/buzzer is controlled from any of 3 sensors/

Hi HG

I will have a decent look at it next weekend, pull some stuff apart and see how i go

Hopefully it is as simple of a bad earth

Regards Don

I just found this thread www.cruisersforum.com/forums/f54/yanmar-waterproof-warning-light-47844.html so hopefully the cause might be the same

Regards Don

Nice to hear you found the problem donk

Good stuff Donk Half you're luck maybe in a couple of weeks I can get the old danish beast fired up

I had the same engine in my last boat and one tip I was given was to run them as hard as possible (don't granny them) mine had over 5000hours when I got it and I did another 1000+ with only minor problems. Apparently salt water cooled engines have the thermostat open at about 67C to prevent salt scale forming. This is pretty cool for a diesel so running them hard (2400-2600rpm) helps keep the temp up and not glazing bores etc. Seemed to work for me - it ran like a sewing machine and used less than 1.5l/hr. I loved that engine. I did use to go through impellors rather quickly though (roughly every 100hrs).