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Old 17-07-2014, 16:42   #1
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Yanmar Help!

Hello All,
I am halfway done with an inside passage trip from Seattle to Juneau (in Juneau now, looking to head back south). I have had high temperature issue on my raw water cooled Yanmar 3GMD (1984). there is nothing wrong with the engine other than it starts throw steam out the exhaust above 2000 rpms after running for 15 minutes or more. It does seem to be temperature dependent, as in, on a sunny warm day there is almost no steam. I have a hand help temperature gauge and when i shoot the engine, it reads around 160 degrees on the block, and around 185-200 on the manifold next to the elbow. it is my understanding these engines should run closer to 140, right? this has been an ongoing issue for the last few months, and below are what i have done in attempt to remedy the problem...

-refurbished the water pump
-replaced the through hull strainer
-ran the cooling system with Rydlyme (clean on the inside based on a visual inspection after)
- checked the elbow for blockages, looks good.
- replaced thermostat, and verified it opens at 120 degrees
- water flow looks okay out the back after all this. about 2.5 gallons at 2000 rpm
- replaced zincs
- changed oil
- replaced all oil and fuel filters

at this point i am at a loss. no engine alarms go off when i am running, I am just trying to be proactive about it before i run into a problem. could it be possible the injectors need servicing? the engine runs really smooth at rpm, but I'm wondering if this might lead to overheating? any help would be greatly appreciated! just need the engine for a few narrows on the return trip!

thanks all,
mark-
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Old 17-07-2014, 17:13   #2
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Re: Yanmar Help!

Quote:
Originally Posted by mangata View Post

-refurbished the water pump
-replaced the through hull strainer
-ran the cooling system with Rydlyme (clean on the inside based on a visual inspection after)
- checked the elbow for blockages, looks good.
- replaced thermostat, and verified it opens at 120 degrees
- water flow looks okay out the back after all this. about 2.5 gallons at 2000 rpm
- replaced zincs
- changed oil
- replaced all oil and fuel filters

mark-
2.5 gallons per what period of time?
You don't mention the impeller?
Any signs of water pump belt slippage?
Have you investigated the heat exchanger condition?

If you check the impeller pay close attention to the cover, they can wear and allow water to "bypass" and not get pumped.

Do you have any other devices plumbed into the water system (water heater etc.)?
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Old 17-07-2014, 17:19   #3
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Re: Yanmar Help!

Please confirm if your engine is cooled directly by sea-water (raw water cooled?) or if it has a heat exchanger?
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Old 17-07-2014, 17:27   #4
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Re: Yanmar Help!

From the OP's post, the engine is raw water cooled. There is a product called 'Salt Away', I believe, that is supposed to remove salt incrustations. Raw water diesels must be run at cooler than 160 F, IIRC, or salt deposits will build up in the engine. If that is/has happened you'll need to clean out the engine with something that will dissolve those passage blocking salt buildups.

Could your problem be that you are now sailing in much colder waters and it's just condensation from the cooler air/water not really steam??
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Old 17-07-2014, 17:27   #5
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Re: Yanmar Help!

Sorry for the lack of specifics! to answer your questions...
2.5 gallons a minute at 2000 rpm. I know my engine is supposed to spit out 3gpm @ 3400, so it seems pretty good on flow.

By "refurbishing the water pump," I mean I replaced the impeller, baking plate, shaft seal, belt, and gasket. no slippage and no drips.

There is no heat exchanger, as it is a raw water cooled system. there was a bit of salt buildup, but the Rydlyme cleared all that out very well (I was very impressed). also, as a result of having no heated coolant, no thermal thieves in the system.

mark-
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Old 17-07-2014, 17:36   #6
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Re: Yanmar Help!

rover,
I tried salt away with no luck. not very strong stuff. Rydlyme was the way to go. biodegradable and effective (they have a demo of it dissolving a shell in the palm of a hand) really would recommend it. I ended up doing a complete flush for 4 hours with the T-stat removed and it hooked up to the intake and output of the system, with a pump circulating it constantly. after this, I cannot see any rust or calcium deposits in the system. looks brand new.

as for the colder water / weather, it definitely has an effect on the amount of steam, but the 160 temp taken off the block concerns me for the reason you mentioned... quick calcium buildup in the system...
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Old 17-07-2014, 17:46   #7
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Re: Yanmar Help!

Presumably you don't have a baseline for the engine temp. before you experienced this "problem".

Is there any difference in the block temps on the good days compared with the bad days?

If not, then I think Roverhi is probably correct in thinking "it's just condensation from the cooler air/water not really steam".

Technically speaking however, it must all be condensation as steam is not visible.

BTW, I wasn't aware of Rydlyme, thanks for the information
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Old 17-07-2014, 17:52   #8
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Re: Yanmar Help!

I'm wondering about the relationship between outside engine temperature readings and the temp of the coolant inside? I have never seen any data to support the idea that if the IR meter shows say 180 F then the coolant must also be at that temperature.

Anyone actually know anything about the thermodynamics of this?

And also, have you checked the IR meter's accuracy? I have two of them, and they often disagree significantly.

Cheers,

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Old 17-07-2014, 17:53   #9
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Re: Yanmar Help!

well regardless of the stem / condensation sign... shouldn't the engine be running cooler than 160?

and I'm glad to spread the word about Rydlyme, just be sure to get their marine version. =)
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Old 17-07-2014, 18:00   #10
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Re: Yanmar Help!

hey jim,
that is a good point... the water alarm is not going off, so i assume the temperature inside the block is cooler than war the IR is reading on the exterior. and it seems pretty accurate, but ill have to check against another gauge to be sure.

I would love if I didn't have an issue, and it was all in my head. I just don't see any other sailboats steaming anything like what I do when they pass me on calm motoring days. the steam has been my worry, as this is my third boat with a yanmar 3gm, (first raw water cooled), but they have never steamed so much before.

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Old 17-07-2014, 18:09   #11
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Re: Yanmar Help!

What is the water temperature at discharge. Did you check the raw water thru hole for a blockage. Have you verified that the thermostat is opening at 130-140 and not 160-170. (in a pan of water on the stove).

2.5 GPM is more the adequate to cool a 3gm at 2000 RPM. There is twice the BTU capacity.

My guess is the Tstat is not working or the wrong temp range. Either the bypass part is not sealing or it's the wrong temp range. Your temperature readings match my 3gm30f, So I'm thinking T-stat.

You are correct that the raw water cooled engines should be running at 130-135 max. Any higher will cause excessive liming in the engine passages.

I'm actually not too concerned with the steam out the exhaust, with the cold water temps and dew points, your probably just making fog, not steam. Verify that the water temp of the exhaust is under 140 degrees F.

Edit: Might pull each decompression lever one at a time and verify that all cylinders are equally loaded. A blown head gasket, might cause steam and higher temps, but only local to the effected cylinder. I assume it starts fine?
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Old 17-07-2014, 18:16   #12
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Re: Yanmar Help!

sailorchic,
I have checked for blockages on the through hull, and nothing. I wasn't even hauled out a week ago for anther reason, and visually saw it was clear of debri.

the outlet water temp is pretty hot when the engine is up to temp. havent shot it with the IR, but its in the ballpark of 110 degrees.

aslo, yes, I was worried that the replacement thermostat I found was for a raw water system (lower opening temp), so i verified it opened at 130 before putting it in. I was hoping that was the issue, but no such luck.

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Old 17-07-2014, 18:21   #13
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Re: Yanmar Help!

so, i may be mistaken, but is the 140 degree operating temp for the engine, or the water temp inside the system? could it be possible the block is operating at 160 while the water is at 140 and okay?
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Old 17-07-2014, 18:27   #14
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Re: Yanmar Help!

sailorchic,
I did checked each cylinder by pulling the decompression levers, and they all seem to have the same effect on the engine. it also starts within the one or two turns (very fast) with little to no smoke out the back. it also doesn't produce any signs of smoke or steam or anything until it is loaded for 15 min at 2000 at least.
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Old 17-07-2014, 18:32   #15
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Re: Yanmar Help!

I would expect the head top and sides will be hotter then 140 degrees due to heat transfer in the head. If you can shoot/measure the temperature on the back plate on the block (where your engine zinc is located BTW) that will give you the back of the water jacket.

The outside of the manifold will also be hotter due to exhaust gases.

Personally if the discharge water temp is 110 degrees F, you have no issues. Part of that is heat from exhaust gases. Raw water engines will smoke, actually fog more the a fresh water cooled engine in cold climates. It just depends on water temperature and dew point and you will make fog. No way it's steam unless its above 160-170 which is where flash steam starts. At 110 degrees, it's fog, as it disappears under sunny conditions. Steam would not disappear.
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