Yanmar Water Temp

[RAD88]

I have a YSB12. It only has idiot lights. How do you know when the thermostat has opened? I just winterized the boat in a slip on Christmas eve and could not tell when the thermostat had opened to put in the anti-freeze. The raw water only got luke warm at best and I ran the engine at 3/4 throttle for 20+ minutes. The thermostat works - I checked it in a pan of boiling water at home.

Does anyone know if the threads on the Yanmar water temp sender and oil pressure sender are compatible with other gauge manufacturers. I wold love to replace the idiot lights with working gauges and end the guess work.

 

[Ralph Johnstone]

Can't speak from first hand experience on the YSB12 but can tell you that the 2GM20F sensor plug for the oil pressure was NOT NPT. Yours is probably the same as the engine is metric. Couldn't get under there to determine what the thread was. Simply chased the old threads with a 1/8" NPT pipe tap. Nice tight fit so I knew I'd cut a complete new thread. Cleaned the thread thoroughly with a greased Q-tip to ensure all cuttings were removed as this point is after the filter.

Never did find a good point to take the water temperature so used a grounded brass T in the water discharge line (to the domestic hot water heater) to insert a sensor.

 

[Bill Roosa]

Hey Rad88
You really don't have to manage the engine coolant that way. After filling it with 50/50 mix close the cap and fill the overflow bottle to the "Full Hot" line. Write yourself a note and attach it to the ignition key to remind yourself to check the coolant BEFORE you start the engine next spring. It is a little known fact that the temp in the boat engine space varies over the course of time and those changes cause the coolant to be sucked into the engine and air to be forces out. After you check the coolant (and refill it to the hot mark, it WILL be lower) write yourself a note to check the coolant lever after the engine is cold/before you start it again then start the engine as normal and go sailing. Any small amount of air will get forced to the overflow bottle and coolant will get sucked back in to completely fill the engine.

Can't help on the sensor threading.

 

[kloudie1]

Rad, it is best to remove the thermostat when winterizing. This will get plenty antifreeze into the block and head with the bypassing caused by the thermostat.

Bill, that engine is raw water cooled, so he has to get antifreeze into the block to replace the sea water..

 

[RichH]

Does anyone know if the threads on the Yanmar water temp sender and oil pressure sender are compatible with other gauge manufacturers. I wold love to replace the idiot lights with working gauges and end the guess work.

The 'instrument sender' connections on Yanmars are metric.
You can simply put a 'tee' into the engines oil and water temp. sender ports .... and operate both gages and idiot lights. The best gage set up is an electronic 'sender' at the engine wired to an electronic gage readout mounted to where you can easily see it.
Most auto supply shop gages, 'instrument sending units', etc. these days are metric thread profile.

 

[joker460]

You can get the adapter here or at any auto racing store:

https://www.pegasusautoracing.com/productdetails1.asp?RecID=56

On the 3GM30 there is a spare oil port were I mounted mine.

For water temp, depending on how your system is plumbed. If you search this site you will find different sizes:

https://www.pegasusautoracing.com/p...//www.pegasusautoracing.com/keywordsearch.asp

 

[Jalepeno]

Your YSB12 is almost the same as my YSM12. They are metric motors but NTP fittings will fit with a bit of Teflon tape.
We use our boat all year round and have no need for “winterising” in our mild and wet climate. If I ever needed to, I would just drain the raw cooling water using the drain cock under the cylinder. The cooling water is only around the cylinder liner and in the cylinder head. If draining the cooling water, make sure the drain cock is not blocked with sediment (use a small screwdriver). You should get about ½ litre (2 cups) of water to drain out. You may need to get the water out of the water pump, hoses and water lift muffler. Make sure your zinc is in good shape.
We are still dreaming of a white Christmas.

 

[rardiH36]

Does anyone know if the threads on the Yanmar water temp sender and oil pressure sender are compatible with other gauge manufacturers. I wold love to replace the idiot lights with working gauges and end the guess work.

Hi Rad:

Re-reading your opening post ... at the risk of stating something you might already know .... I would like to suggest be sure to think through this conversion.

Firstly, the OEM Yanmar temp sender (actually it is a switch) also activates an audible alarm when the temp gets just a few degrees above the sea water model's ~140F. The thermostat is also a 140F variety. If you change out the switch for a temp gauge sender, you won't have the alarm if the temp begins to rise over the ~140F (unless you can find a system with a settable alarm). Maybe you will look at the temp gauge every minute or so when motoring, but I know that I couldn't. So think about keeping the idiot system and adding an independent temp gauge. This is what I did. Because you have a seawater cooled engine (mine was too, but Hunter modified it to anti-freeze + external heat exchanger), it is important to have the 140F switch. If salt water gets much above 150F, minerals and salt will deposit in the engine's coolant channels. This can't be reversed easily. I mention this because the normal anti-freeze cooled Yanmar's have a thermostat and matching alarm switch at about 170F instead of the raw water's 140F set. In my case, a PO replaced the 140F switch for a 170F one which escaped my attention. (Maybe because the 170F that was stamped on the side of the switch was about microscopic small and facing in the wrong direction?). I once forgot to open my raw water seacock. The alarm did not go off. Fortunately, because my engine was converted to anti-freeze, the 5-7 lb pressure cap vented --- alerting me to the overheat before it became critical. I now have the correct 140F alarm switch to match the 140F thermostat.

 

[Charles Erwin]

The thermostat is 105F on a raw water cooled motor - not 150F. With raw water cooling and a 100 -250 guage it is unlikely you will see the needle on an aftermarket temperature gauge move at all.

Tapered threads on Yanmar motors are British Standard Pipe (many refer to BSP as "metric") BSP threads do not match US standard called NPT (National Pipe Thread) either in threads per inch nor in the thread angles. Thus one should use adapters to convert Yanmar BSP ports to accomodate NPT senders.

Charles

 

[rardiH36]

The thermostat is 105F on a raw water cooled motor - not 150F.

Charles

Good observation. But I think we are both right. My 2QM20 manual is on my boat so I can't double check that. However, I do recall a thermostat spec in the 140F range.

I do have at hand a GM series manual. (My PO had this on board instead of the QM series manual which is the engine on the boat!)

Here's a pic of the Yanmar service manual temp switch spec's for both the GM series fresh water (self contained anti-freeze) and seawater versions. The alarm goes off between 148F and 154F. Resets (turns off again) and 140F. I know that for the QM series, the switch has a yellow instead of a white dot. The yellow dot version alarms about 10F lower than the GM's white dot one. This I think is the reason that my QM temp alarm sometimes goes off. Thermostat operates nearer the 140F. Alarm switch triggers not much higher. This happens after I've run the engine for a while, then shut off for a few minutes, then restart. I think that without the coolant water flow, the core heat from around the cylinders radiates into the block and heats above the alarm switch trigger point. After a minute or two of resumed operation and coolant flow, the alarm stops. I have been thinking about getting the higher threshold GM switch to replace the one that I have.

Also attached is a pic of the the GM series raw water thermostat spec. Yes closer to your 105F.

Anyway, not withstanding the actual degrees F's, my previous comments about being careful about doing any alarm / sensor conversion still applies, I think.

And yes, my temp gauge pointer doesn't move up much. Only to about 130F or so. But it's handy to have because if the alarm goes off, I can look at the gauge to verify that the engine is not overheating.