1GM10 Engine Wire Harness

[jamieFL]

I cleaned, derusted, painted, and replaced routine maitenance parts on my 1GM10. I took photos of everything I disconnected, but wouldn't you know it... I have a plug I don't know where to plug in. Please see photos.


Mystery Plug

After

Before

 

[Ron20324]

That looks like a plug to go to a SailDrive engine setup. My 2006 3YM20 has it . It comes up on the engine cockpit panel as an alarm, so I always wonder if it could be used for something else. Has anyone tried to use it for maybe a bilge water level or anything???

 

[jamieFL]

I don't have sail drive. I don't think it was plugged to anything, but it does look a little too clean for that. Unfortunately, I didn't document where it came from.

 

[jamieFL]

Yes. I think you are right. It is for the saildrive water sensor. Thanks. I was able to confirm, knowing what to look for.

 

[StargazerP303]

Jamie, Here are some manuals for 1GM10.
I have others to send but too big.. PM me your email..
Regards, Capt. Rob

 

[jamieFL]

I'd like to ask an unrelated question. The PO of the boat removed the thermostat. By the amount of buildup on the thermostat housing, it has been that way for a while. Is there a reason for that, or did he cheap out because he didn't want to spend $50 on a new thermostat?

I cleaned everything up and have one on order. I'm just wondering, since it ran great without it, there could have been a reason he left it that way.

 

[markwesti]

We have a 2QM 15 and it is fresh water cooled . In the past I have removed the thermostat when trying to track down over heating problems . I left it out for awhile and it made no difference , I was still over heating . So I finally got the over heating fixed and I put back in the thermostat . I was talking to a mechanic he told me the thermostat does two things , first obviously it stays closed in tell the engine gets up to temp , second it acts as a regulator so the cooling water does not move too quickly and lets the heat exchange process take place . I think it is important to have one . My over heating cause , hard salt build up at the raw water thru hull . Always the last place you look .

 

[Charles Erwin]

I'd like to ask an unrelated question. The PO of the boat removed the thermostat. By the amount of buildup on the thermostat housing, it has been that way for a while. Is there a reason for that, or did he cheap out because he didn't want to spend $50 on a new thermostat?

I cleaned everything up and have one on order. I'm just wondering, since it ran great without it, there could have been a reason he left it that way.

Jamie -

Some comments you will get here are from people who have "fresh" water cooling - systems that use a heat exchanger. Your motor is direct sea water cooling - there is no heat exchanger and yours works different.

In your case the thermostat controls whether the sea water flow goes through the motor thence overboard, directly overboard, or some of both. If there is no thermostat then temperature control is absent and your motor never gets up to its design operating temperature. Installing a thermostat will permit the motor to run at a higher temperature however the thermostat opening temperature needs to be relatively low otherwise the sea water salts will 'drop out' and accumulate (in the form of hard scale) in the motor cooling passages.

In short we need a thermostat because we want higher operating temperature and that promotes more efficient motor operation. But not too high because we don't want sea water deposits which will restrict flow due to the accumulation of salt water scaling.

Look it another way - Yanmar engineers would not have spent millions on designing a thermostatically controlled sea water cooled system if they thought you could get by without one.

Charles

 

[kloudie1]

The Yanmar thermostat for your engine is part# 105582-49200, and is around $36.. The size is unique to Yanmar so you'll have to buy it from them. I second Charles's note.. If the motor is overheating, the thermostat may not have been the problem and a new one should be installed.. if the engine then overheats, the cause of the problem should be fixed.. raw water pump, piping, impeller condition.. clean thru-hull intake, etc..

If the mystery plug wires are a red-white and a black, that is an unused saildrive water detector connector..

 

[jamieFL]

I bought a genuine yanmar thermostat for 1gm10 raw water systems,

https://shop.toadmarinesupply.com/ships_store/index.php?p=details&mfc=Yanmar&sku=105582-49200

so I will be putting it in.

Before I started, I ran 50% vinigar solution through the engine for about an hour, then 2 cups bleach in 4 gallons of water for about half an hour, then fresh water for half an hour. The first 2 stages of water turned cloudy and there were deposits in the buckets, so it did some good. There are still some deposits in the smaller bronze t fitting. See photo and zoom in. I was thinking of running a drill bit by hand through the t fitting. Good idea, or bad? I soaked the water pump housing... I rebuilt the pump...and thermostat housing in ospho, so they are clean. The large passage seen through the zinc port looks completely clean. I have no ideas about the smaller passeges in the head. I'm assuming they will be similar to what you see in the t fitting. There were no overheating issues before hand. Hopefully there will be none when the thermostat goes in.

 

[jamieFL]

Back to the extra plug. If it is hooked up to an unused light on the control panel, could I hook it up to a float switch and use it as a high water alarm?

 

[Charles Erwin]

Sure - just need the lamp in the control panel. But - it will only work when the ignition is ON. See your private messages and the B version wiring diagram.

Charles

 

[jamieFL]

In that case, that would be a bad idea for a sailboat.

 

[Alan Gomes]

Jamie -

Some comments you will get here are from people who have "fresh" water cooling - systems that use a heat exchanger. Your motor is direct sea water cooling - there is no heat exchanger and yours works different.

In your case the thermostat controls whether the sea water flow goes through the motor thence overboard, directly overboard, or some of both. If there is no thermostat then temperature control is absent and your motor never gets up to its design operating temperature. Installing a thermostat will permit the motor to run at a higher temperature however the thermostat opening temperature needs to be relatively low otherwise the sea water salts will 'drop out' and accumulate (in the form of hard scale) in the motor cooling passages.

In short we need a thermostat because we want higher operating temperature and that promotes more efficient motor operation. But not too high because we don't want sea water deposits which will restrict flow due to the accumulation of salt water scaling.

Look it another way - Yanmar engineers would not have spent millions on designing a thermostatically controlled sea water cooled system if they thought you could get by without one.

Charles

Correct me if I'm wrong (and I could be), but I don't think the thermostat on a 1GM/1GM10 works quite that way.

When the engine is cold, the raw cooling water flows straight from the pump and directly into the exhaust elbow, bypassing the engine block altogether. As the engine heats up, the thermostat opens, blocks the straight path to the exhaust elbow, and then shunts the cooling water through the block and out the exhaust elbow through that path.

I believe that what would happen with no thermostat is that, without the diverter function of the thermostat present, most if not all of the cooling water would tend to dump straight into the exhaust, i.e., the "cold" position, and little would find its way through the block. This would actually have the effect of *decreasing* the cooling flow through the block, not increasing it.

Again, correct me if I've got that wrong, but I believe that's how it works in the case of the 1GM/10.

Either way, you should replace that thermostat!

 

[Charles Erwin]

Alan reasons that flow absent a thermostat would " . . . . . have the effect of *decreasing* the cooling flow through the block, not increasing it."

The thermostat has two jobs. At start up it makes the motor get warm quickly - it is shut-at-cold to prevent flow through the block and so the motor temperature rises when the motor is cold. The bypass is open because we cannot shut off the water flow from the seawater pump. We need the bypass to expel the water thus water pressure does not blow out the various seals in the cooling system - including the pump seals - when the motor is cold. The thermostat also makes the motor get cooler when it is hot. It is full open when the motor is hot - just the same as if the thermostat had been removed . The bypass is closed at hot because the water has another path overboard and so over pressure relief is no longer needed.

So to the question -- first there is no doubt some water bypasses the block when there is no thermostat -- but if all the water did then Jamie's motor would constantly overheat - yet it does not. I think the reason is this. The seawater pump passes water to a tee where the flow divides. One path leads to the motor block and the other to the thermostat housing (bypass.) The passage to the block is about .440" diameter and the bypass is about .270". Since liquid flow is proportional to the 4th power of the difference in the radius between these two paths - considerably more water passes through the block than through the bypass (by a factor roughly 7 times - theoretically) even though the bypass is open. When the thermostat is removed the amount or water going through the bypass is surprisingly quite small whereas that going through the motor is relatively large and that is because the designers made the passages different sizes.

Anyway that is my story and I am sticking to it for the time being.

Charles

 

[Alan Gomes]

Alan reasons that flow absent a thermostat would " . . . . . have the effect of *decreasing* the cooling flow through the block, not increasing it."

The thermostat has two jobs. At start up it makes the motor get warm quickly - it is shut-at-cold to prevent flow through the block and so the motor temperature rises when the motor is cold. The bypass is open because we cannot shut off the water flow from the seawater pump. We need the bypass to expel the water thus water pressure does not blow out the various seals in the cooling system - including the pump seals - when the motor is cold. The thermostat also makes the motor get cooler when it is hot. It is full open when the motor is hot - just the same as if the thermostat had been removed . The bypass is closed at hot because the water has another path overboard and so over pressure relief is no longer needed.

So to the question -- first there is no doubt some water bypasses the block when there is no thermostat -- but if all the water did then Jamie's motor would constantly overheat - yet it does not. I think the reason is this. The seawater pump passes water to a tee where the flow divides. One path leads to the motor block and the other to the thermostat housing (bypass.) The passage to the block is about .440" diameter and the bypass is about .270". Since liquid flow is proportional the the 4th power of the difference in the radius between these two paths - considerably more water passes through the block than through the bypass (by a factor roughly 7 times - theoretically) even though the bypass is open. When the thermostat is removed the amount or water going through the bypass is surprisingly quite small whereas that going through the motor is relatively large and that is because the designers made the passages different sizes.

Anyway that is my story and I am sticking to it for the time being.

Charles

Thanks, Charles!

 

[jamieFL]

Yes. Thanks for all the great info.