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

Select to expand quote

Donk107 said...
[br]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

If it was mine engine Id remove the thermostat and test it in boiling water for
a saucepan perhaps the thermostat may not be operating correctly . one possibility the thermostat may have closes shut or reduced it opening while running and restricted its flow and then it has opened again . thats one that comes to mind

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

from this page
http://forums.sbo.sailboatowners.com/printthread.php?t=121216

On my bukh I drained the engine block and filled it with vinegar for a week and did it again . my engine is a cast iron engine you would have to check on your as I have a feeling its aluminum < is a land mechanic
Even after I soak her in vinegar I still had to turn some of the pen anode off to get it in there I scraped and scrubbed it there

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.
.

Select to expand quote

drpete said...
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.
.

Your probably right Dr Pete

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

Select to expand quote

Donk107 said..

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 wonder where the audible alarm gets its power could any thing else be giving power Donk? Does the boat have a temp gauge and a temp light/ alarm . Is that the standard Buhk engine panel? How many gauges does the panel have Donk ?
Ill have a look in the Bukh Bible schematics here see what I can suggest

Select to expand quote

HG02 said..

Donk107 said..

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 wonder where the audible alarm gets its power could any thing else be giving power Donk? Does the boat have a temp gauge and a temp light/ alarm . Is that the standard Buhk engine panel? How many gauges does the panel have Donk ? Ill have a look in the Bukh Bible schematics here see what I can suggest

Hi HG

Thanks for that but my engine is a Yanmar not a Buhk

Regards Don

Oh forgot Found the panel on page P47 for a Bukh
On the Bukh it has three diodes on the back of the engine panel if one of those burns on it can cause similar problems
I agree with you Donk something in the engine control panel Might be similar to the Bukh three diodes

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

Hi
This is parts list if perhaps you don't have it.....j30.us/files/Yanmar-2GM20-Parts-List.pdf

But no schematics . Guess this might be one... Confirm.
If this is a right schematic, than buzzer sensing over temperature and oil pressure / plus seal on sail drive/

My suggestion what is your problem, not enough oil pressure.
Could be easily related to oil pump, but more likely wear of the engine, pressure can't build up.
But it's a matter of more testing to confirm.

Select to expand quote

Donk107 said..



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


Any thoughts

Regards Don

It would seem to me the logical thing to do would be to isolate and remove power from that feature of the control panel circuitry.

Hi Charriot

Thanks for that

The wiring diagram you posted does not show a common earth between the tacho sender and the saildrive sender like the one i found on the net does, but yours looks like how i imagine the one on my boat would be ( i have a engine manual on the boat so i will look at it next time i am out and see if it has a wiring diagram in it to see which one is correct)

I dont think it is a low oil pressure problem because as i said the sail drive light flashes in unison with the buzzer and there is no low oil pressure light flashing but i will start it with the pressure sender wire disconnected next time i am out on it to confirm this

Also the buzzer chirps faster as the revs increase where as if it had low oil pressure i would have thought the higher the revs the pressure would improve

Also something else today i noticed is that when i had run the engine for a while and shut it down (key in the off position) there was a high pitched noise coming from the buzzer that stopped when i operated the panel light switch (i actually think i stopped it by turning the switch to the on position so i wonder if this was creating a earth circuit)

It would be interesting to see if the chirping when running and the saildrive light flashing stops if i turn the panel light switch on while it is running

Regards Don

Select to expand quote

cisco said..

Donk107 said..



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


Any thoughts

Regards Don

It would seem to me the logical thing to do would be to isolate and remove power from that feature of the control panel circuitry.

Hi Cisco

If i removed the bulb for the sail drive light i think it would find another circuit to earth through

Regards Don

Select to expand quote

Donk107 said..

cisco said..

Donk107 said..



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


Any thoughts

Regards Don

It would seem to me the logical thing to do would be to isolate and remove power from that feature of the control panel circuitry.

Hi Cisco

If i removed the bulb for the sail drive light i think it would find another circuit to earth through

Regards Don

I wonder what would happen if you disconnected the audible alarm Donk anhd tested the circuits form there back as it appears to connected to all three warning circuits also the wiring harness by the diagram Charriot put up has a plug Id pull it apart and check the connections in there also

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/

Removing globes don't affect any function of the engine.
Disconnecting any or all wires don't affect any functions .

Globes and buzzer is only info to keep engine in safe condition
Warning only.

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

Hi Charriot

If it has not got a sail drive sensor where do you think the sail drive circuit is finding its earth to bring the light on ?

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

Hi to all

I went out to the boat today ,removed the steps to access the engine and moved the wiring harness that the saildrive sensor wire runs in and when i started the engine and let it run at various revs the beeper was quite and the saildrive sensor light was not flashing so hopefully i have sorted it

I looked at the exposed wire but i could not see any obvious rubs through the insulation so it is a bit of a mystery

While i had it apart i found that the manual bilge pump suction hose had split and that i was getting sea water running into the bilge when the engine was running so i spent a couple of hours tracking down where the water was coming from and i eventually found a hose clamp on the exhaust water trap inlet side was a bit loose so i tightened it and it appears to be fixed as well

I was hoping to go for a sail today but as you can see from the pic below there was a lack of wind

Regards Don

Nice to hear you found the problem donk

Select to expand quote

HG02 said...
Nice to hear you found the problem donk

Hi HG

Not 100% percent sure but i ran it a dozen times while i was trying to fing where the sea water was coming from and it didn't make a noise so fingers are crossed

Regards Don

Select to expand quote

Donk107 said...

HG02 said...
Nice to hear you found the problem donk

Hi HG

Not 100% percent sure but i ran it a dozen times while i was trying to fing where the sea water was coming from and it didn't make a noise so fingers are crossed

Regards Don

Hi to all

No wind today but the weather was nice so we went for a motor up and down the river

We were motoring for a couple of hours at various revs and no noise from the beeper so i think it is sorted

Thanks to all who contributed to the thread

Regards Don

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

Hi HG

Is she still out of the water

Regards Don

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).

Select to expand quote

Donk107 said...
Hi HG

Is she still out of the water

Regards Don

No she just swinging on the mooring Donk Im to busy with my projects to be bothered sailing Thats what it seems like

MMMMMMMMMM maybe I forgot that's why I bought her This spring she will ll have some sails up I promise

Select to expand quote

Donk107 said...
Hi HG

Is she still out of the water

Regards Don

Hi HG

What do you need to do to make her run

Regards Don