Yanmar 3GM30 - how much smoke is OK?

[akio.kanemoto]

Originally Posted by delmarrey

In colder climates, probably yes. But then it comes down to your thermostat. Raw water cooled can vary.

So is my 154.4F too hot or too cold? I'm in Sydney Australia at the moment - so not too hot or cold.. but will be going to the tropics.

Thanks again!

[akio.kanemoto]

Originally Posted by delmarrey

The Yanmar 3JH manual recommends that the motor needs a cool down period. Also just before shut down that one rev's it 4-5 times (but not hold it at hi rpm's) before shut down to blow carbon out of the system.
I'd check your manual to be sure.

I have the service manual, but not the operation manual, I'll look through it and see if I can find something.

There's some interesting info here:

Yanmar Marine Engine Help

But it states things like I should be running at 2900rpm all the time etc... (isn't this a bit high?) - so the page could be suspect?

[delmarrey]

Originally Posted by akio.kanemoto

So is my 154.4F too hot or too cold? I'm in Sydney Australia at the moment - so not too hot or cold.. but will be going to the tropics.

Thanks again!

Can't say to be absolutely sure but it's so close to the water temp, I myself would not worry. What does the temp gauge say at the helm?

[delmarrey]

Originally Posted by akio.kanemoto

I have the service manual, but not the operation manual, I'll look through it and see if I can find something.

That's just a name thing, but yeah!
There's some interesting info here:

Yanmar Marine Engine Help

But it states things like I should be running at 2900rpm all the time etc... (isn't this a bit high?) - so the page could be suspect?

For prolonged running, a pleasure boat engine a good operating speed is around 85% of maximum continuous rated RPM (see the engine data plate)
assuming the propeller size is correct and the engine can reach maximum rpm).
See this list for approximate rpm:

That means run max. cont. at 2900 RPM's, but not for long. 85% of that for cruising speed. I run at about 2600 myself @ 7-7.5 kts.

[akio.kanemoto]

Originally Posted by delmarrey

Can't say to be absolutely sure but it's so close to the water temp, I myself would not worry. What does the temp gauge say at the helm?

I just have a Yanmar "Type B" panel, so no temp gauge... I just read somewhere that a diesel is supposed to run at 131F and since mine is running at 154F, that it was too hot. (...and now that I have an IR temp gun, I'm checking everything and being extra paranoid!

[akio.kanemoto]

Originally Posted by delmarrey

That means run max. cont. at 2900 RPM's, but not for long. 85% of that for cruising speed. I run at about 2600 myself @ 7-7.5 kts.

So you run at 2600 for long distances as well? I.e. day(s)?

I see a lot of posts stating 1800'ish rpm long term, and the engine does sound comfortable there, but looking at the power curve diagrams, the engine is nowhere near max HP at that level... so is it good for the engine or not?

Whereas at 2500-2600, it is around 85% of max rpm (which is at 2800rpm for the 3gm30).

[delmarrey]

Originally Posted by akio.kanemoto

I just have a Yanmar "Type B" panel, so no temp gauge... I just read somewhere that a diesel is supposed to run at 131F and since mine is running at 154F, that it was too hot. (...and now that I have an IR temp gun, I'm checking everything and being extra paranoid!

It's the water temp you have to be concerned about. Mine runs at 180º F most of the time. If you have a good sender your panel would be showing an alarm if it were over heating. Use the IR gun on the water outlet side of the thermostat housing.

So you run at 2600 for long distances as well? I.e. day(s)? Yes!

I see a lot of posts stating 1800'ish rpm long term, and the engine does sound comfortable there, but looking at the power curve diagrams, the engine is nowhere near max HP at that level... so is it good for the engine or not?
Those are probably larger motors.


Whereas at 2500-2600, it is around 85% of max rpm (which is at 2800rpm for the 3gm30).

That will keep the motor running a long time. Diesel's luv to work and at long hours @ 85% load.

[FuzzyFeat]

The gray smoke is un-burned diesel. Your engine is running cool if the temp is 150 deg. The engine is capable of putting out ~ 27 HP and your load is
way below that (I guess about 5 HP). Your exhaust system will eventually load up with carbon. Charging batteries is an engine killer, even with the refrigeration load you are using a small fraction of what the engine can put out at that RPM. Diesels NEED a full load to be hot and happy.

ALSO 2900 RPM is not high. I ran mine at 3000 all day for years and never had any problems. Kept the engine loaded, hot and happy.

[akio.kanemoto]

Originally Posted by delmarrey

It's the water temp you have to be concerned about. Mine runs at 180º F most of the time. If you have a good sender your panel would be showing an alarm if it were over heating. Use the IR gun on the water outlet side of the thermostat housing.

That will keep the motor running a long time. Diesel's luv to work and at long hours @ 85% load.

Thanks for that - I always thought that the stated 131F/55degC was of the engine block itself! OK, will check the outlet of the thermostat! I'm positive that the exhaust water that it coming out is nowhere near that temperature though!

[delmarrey]

Originally Posted by akio.kanemoto

I'm positive that the exhaust water that it coming out is nowhere near that temperature though!

It shouldn't be! That's what the exhaust mixing elbow is for, to cool the water before entering the hoses.

[sailorchic34]

For a fresh water cooled engine the 154 degrees F would be cool. BUT.. For a raw water cooled engine that would be a little hot. Raw water cooled engines want to be kept below 140 degrees to keep the hardness from building up on the engine parts. Above 140 degrees, the higher the temp the more deposits drop out of the water.

Also at 154 degrees your close to the point where water will start to flash. So that smoke could be flash steam which depending on dewpoint would start to be visible around that temp. Check your thermostat and make sure it opens at about 130-135 degrees or lower...

[akio.kanemoto]

Originally Posted by sailorchic34

For a fresh water cooled engine the 154 degrees F would be cool. BUT.. For a raw water cooled engine that would be a little hot. Raw water cooled engines want to be kept below 140 degrees to keep the hardness from building up on the engine parts. Above 140 degrees, the higher the temp the more deposits drop out of the water.

Also at 154 degrees your close to the point where water will start to flash. So that smoke could be flash steam which depending on dewpoint would start to be visible around that temp. Check your thermostat and make sure it opens at about 130-135 degrees or lower...

Thank you for your reply.

OK, I'm a little confused now - are you referring to the engine block temperature or the water temperature?

My engine block temperature (measured with IR gun next to the anode on the side) is 154.4F, I haven't measured the water itself yet.

Also, I'm a little confused by the terminology regarding "flashing" - the boiling point of water is 100degC (212F)?

[delmarrey]

Originally Posted by akio.kanemoto

Thank you for your reply.

OK, I'm a little confused now - are you referring to the engine block temperature or the water temperature?
Normally when talking about motor temps it has to do with the water temp.

My engine block temperature (measured with IR gun next to the anode on the side) is 154.4F, I haven't measured the water itself yet. You may want to invest in an actual temp gauge.

Also, I'm a little confused by the terminology regarding "flashing" - the boiling point of water is 100degC (212F)?

This is something that is more common in warm waters but if there are restrictions in the flow system the water flow may not be enough to keep the cylinders cool.
So when the water hits the cylinder walls, especially under a vacuum, it'll flash causing steam. The water flow should be under pressure from the pump into the block, so vacuum should not be an issue. But if there is a restriction getting out it may cause over heating.
After determining the actual temp you may want to pull the blocks water pump and have a look inside to see if there is much build up. It's a catch 22, the hotter the motor is, the faster the build up, like what Sailorchic stated.

[sailorchic34]

You are correct that the boiling point of water is 212 at standard atmospheric pressure. However if you watch a pot boil you will note steam/water vapor rise long before the water boils. This is whats called flash steam and starts to happens around 160 degrees F.

Check your water temperature, Though I would expect the block temperature to be near the water temperature, if there is a water jacket behind it.

The discharge water temperature for any raw water cooled engine should be below 140 degrees F. Above 140 degrees the particulate starts to drop out of the water, with more the higher the water temperature. Fresh water systems are closed systems so not much worry about particulate/ liming and they run at a higher temperature.

[roverhi]

It's the salt in the water that begins to come out of the water above a certain temperature. 160 degrees sounds about the temp so you want to run well below that. Think my Volvo MD2b used to run at about 140 degrees. It didn't run hot enough to make hot water for the pressure water system. Might want to change the thermostat in the engine to be sure it doesn't overheat. FWIU, when you exceed the precipitation temperature for salt in the water it leaves an insoluble deposit on the metal inside the engine and will eventually block the engine's water passages.

Freshwater cooled engines are best run at temps from 180-200 degrees and some are designed to run higher. Since the cooling systems are closed circuits and pressurized so won't boil until well above 212 degrees.