Yanmar 1GM Overtemp Alarm / Thermostat

[Delawaredave]

Thanks again for everyone's input !

Update: buddy I own boat with went down himself and found out the transmission was out of oil.

He filled it. Now he says boat seems to be running fine, no alarms under load.

Question: Could overtemp and trans oil issues be connected ?

I don't see how - but if it's working....

[Wotname]

Originally Posted by Delawaredave

.....

Question: Could overtemp and trans oil issues be connected ?

I don't see how - but if it's working....

YES.
Oil lubricates and removes heat from the bearing surfaces and dissipates it into the sump etc.- no oil and heat build up is way faster.

[a64pilot]

Originally Posted by Wotname

YES.

Oil lubricates and removes heat from the bearing surfaces and dissipates it into the sump etc.- no oil and heat build up is way faster.

Yes, but he said transmission oil.
I’d say yes as the transmission having a lot of friction is exactly the same as a barnacle encrusted prop.
However I can’t imagine a transmission causing that much friction, and not be ruined in the process.

Most people don’t realize that the only part of an engine that is really water cooled is the cylinder head, the entire rest of the engine, crankshaft bearings, valve train etc is oil cooled, so besides lubrication, oil has a very important job in removing heat from all the rubbing parts of an engine.

[Wotname]

Originally Posted by a64pilot

Yes, but he said transmission oil.
I’d say yes as the transmission having a lot of friction is exactly the same as a barnacle encrusted prop.
However I can’t imagine a transmission causing that much friction, and not be ruined in the process.

Most people don’t realize that the only part of an engine that is really water cooled is the cylinder head, the entire rest of the engine, crankshaft bearings, valve train etc is oil cooled, so besides lubrication, oil has a very important job in removing heat from all the rubbing parts of an engine.

Opps, so he did - my bad
Note to self - don't post while making the first coffee for the day!

[Compass790]

Yep I'm with A64 pilot, scary that your transmission caused your overheat. I'd change the oil again quickly in the gearbox & look how much metal comes out. If they have the same gearbox as our YSM8 they are extremely robust but nothing can survive long without oil.
It musta bin very noisy. I know it's hard to hear anything over a single cylinder Yanmar but ???. I'd put one of those neodymium magnets on your transmission drain plug too. Hope you are lucky & have dodged a bullet

[Delawaredave]

Thanks. Going to change trans oil this weekend. There's no way so much heat could be generated from transmission to pass to motor to overheat, IMHO.

Also, can't see how could be enough drive train drag from trans to overheat engine either.

So my bet is unrelated. Hopefully I won't be back next weekend posting on overheat questions.... Have a great day !

[Delawaredave]

Well this is embarassing.... buddy I own boat with now tells me the alarms were oil pressure, not temperature, his mistake.

Question: the low/empty oil in transmission has nothing to do with the engine oil pressure alarm circuit, right ?

They're two separate systems, two different oil reserviors, right ?

So filling transmission back up with oil might not be solution to our original oil pressure alarms, right ?

#newbie (if you didn't know that already).

[Wotname]

Originally Posted by Delawaredave

Well this is embarassing.... buddy I own boat with now tells me the alarms were oil pressure, not temperature, his mistake.

Question: the low/empty oil in transmission has nothing to do with the engine oil pressure alarm circuit, right ?

They're two separate systems, two different oil reserviors, right ?

So filling transmission back up with oil might not be solution to our original oil pressure alarms, right ?

#newbie (if you didn't know that already).

Correct on all accounts.
Now is a good time to check engine oil, maybe even change it.
Then get a oil pressure gauge (either electric or engine mounted mechanical one) and find out what is really going on. In the short term, you can remove the low oil pressure switch and fit the gauge into the same port or fit a T piece etc

[Wotname]

BTW, we were all newbies once

[Compass790]

Originally Posted by Delawaredave

Well this is embarassing.... buddy I own boat with now tells me the alarms were oil pressure, not temperature, his mistake.

Question: the low/empty oil in transmission has nothing to do with the engine oil pressure alarm circuit, right ?

They're two separate systems, two different oil reserviors, right ?

So filling transmission back up with oil might not be solution to our original oil pressure alarms, right ?

#newbie (if you didn't know that already).

Easy mistake to make as both alarms make the same sound. Ask me how I know?
You learn to check after motor sailing hard on the wind with the engine water intake on the windward side!
You should get a workshop manual as they have a good troubleshooting section. But I can tell you that the oil pumps wear & you need to check their clearances as per the manual specs. That is assuming you have checked oil pressure as per Wotnames post.
Do not assume it's a faulty sender.

[Dymaxion]

Good idea to change all engine fluids upon initial purchase, then start your log with known dates/events. Put a drop or two of oil onto a clean piece of paper towel to gauge color, lighter is better. A drop or two on your finger tips then rubbing them together may show/feel wear debris if bad, but that's not a definitive test. I have a 1GM10 engine too, believe that there is only one warning buzzer, connected to both pressure and temp switches. It should sound as you turn on the key prior to starting as a system check.

Minor point, in filling the transmission pre-measure the amount of oil required, then dump it all in via a funnel and verify level. Saves filling/checking, topping, topping... overfilling. How would I know that you ask, well... There is an issue about how much oil is left in the trans after draining, since the manufacturers spec will be capacity for a dead empty trans. Have fun.

[BobbieGWhiz]

Originally Posted by lockie

I guess you've already looked to confirm acceptable water flow out the exhaust?

You can check the thermostat by heating it in a saucepan of water with a thermometer to see when it opens. If you're still unsure, reassemble the cooling system but leave the thermostat out, run up close to operating temperature, then close the bypass line (use a small vicegrips to squeeze the hose). This way you are guaranteed full flow through the engine, and now you can run it hard to see if the alarm still goes off. If you just remove the 'stat without constricting the bypass almost all the water will go through the bypass and the engine will quickly overheat.

I had a problem years ago that drove me nuts - I checked and replaced impeller, 'stat and hoses, and soaked the passages in vinegar, but still got an alarm after about 20 min at 3/4 revs. I finally rodded the CW seacock and thru hull with a very long screwdriver, and found in there a long hard piece of marine growth the like of which I'd never seen before. I put the old impeller and 'stat back in just to check: good as gold, except for about a hundred bucks and 20 hours of my time down the drain.

Cheers, Graeme

I can’t understand why removing the thermostat would cause the engine to overheat. Putting a vice grip on the cool seawater hose would prevent the exhaust from being cooled as is intended. If all the seawater is directed only to the block then you are preventing cool seawater from reaching the elbow to cool the exhaust. In addition, a removed thermostat should operate in the same way as an opened t-stat with some of the cool sea water mixing with the heated seawater and then moving to the elbow.

[lockie]

Originally Posted by BobbieGWhiz

I can’t understand why removing the thermostat would cause the engine to overheat. Putting a vice grip on the cool seawater hose would prevent the exhaust from being cooled as is intended. If all the seawater is directed only to the block then you are preventing cool seawater from reaching the elbow to cool the exhaust. In addition, a removed thermostat should operate in the same way as an opened t-stat with some of the cool sea water mixing with the heated seawater and then moving to the elbow.

Read my post again: constrict the flow in the bypass line and all the water is directed through the engine. From there it then flows into the exhaust elbow. Sketch the water circuit out on paper and you'll see.


Cheers, Graeme

[Wotname]

Originally Posted by BobbieGWhiz

I can’t understand why removing the thermostat would cause the engine to overheat. Putting a vice grip on the cool seawater hose would prevent the exhaust from being cooled as is intended. If all the seawater is directed only to the block then you are preventing cool seawater from reaching the elbow to cool the exhaust. In addition, a removed thermostat should operate in the same way as an opened t-stat with some of the cool sea water mixing with the heated seawater and then moving to the elbow.

You may not realise the Yanmar thermostat in a raw water cooled engine is not simple OPEN / CLOSED (ON/OFF) operation. It is more like CHANGE OVER (ON/ON) operation.

In the cold position, it diverts all the raw water to the exhaust and very little to the engine. In the hot position, it diverts all the raw water to the engine which then goes into the exhaust and it closes off the bypass. Between cold and hot, it allows some water to the engine and some directly to the exhaust.

At all times, the volume of water entering the exhaust remains the same while the thermostat determines how much of the water travels via the engine.

[BobbieGWhiz]

Originally Posted by lockie

Read my post again: constrict the flow in the bypass line and all the water is directed through the engine. From there it then flows into the exhaust elbow. Sketch the water circuit out on paper and you'll see.


Cheers, Graeme

Correct me, but the more the t-stat opens, the more water can flow through the block, and therefore less of the stream would flow through the bypass. If the t-stat is completely opened, won’t water flow through both paths (in some proportion to the resistance of each path)? The more the t-stat opens, the more water flows through the block. And thus, why wouldn’t a fully opened t-stat be equivalent to a removed t-stat?