Yanmar 3YM30 overheating

[jwilson]

Since near new my Yanmar 3YM30 in a Sun Odyssey 35 has occasionally overheated at high revs. It was an early build engine and has had the later larger heat exchanger fitted under warranty.

The power range at which this overheating occurs is steadily increasing. At first it was only 3000 rpm plus that would cause it (max revs are 3400) and the boat will reach this revs giving about 7.8 knots, so is probably not overpropped. Now it is consistently overheating after a period at 2900 and on one occasion after an hour at 2500. It's not just the alarm, the engine is overheating.

As I regard cruising revs to be 2400-2900 - if the engine is on it's because you want to get somewhere - this is unacceptable. This rev range translates to around 5 - 6.5 knots.

In the last ten days with the assistance of a Yanmar service agent engineer I have had a complete new raw water pump fitted, a new temperature sensor, and the heat exchanger insides look clean. Also tested the engine with the thermostat removed. Still overheats given high power running, though lots of water is clearly circulating and coming out of the exhaust.

I suspect that others with this engine have the same problem but may not know it, as they rarely run their engines hard enough.

The engine manufacturers UK distributors told me at last years Southampton Boat Show that they do not know of any overheating problems with this engine. As they paid for the heat exchanger to be changed on mine and at least two others I know of, this is obviously not true, but they stuck to their story that no-one else had a problem.

If you have a 3YM30 that overheats, please PM me.

If you have a 3YM30 that has never overheated, but only ever run at 1800-2500 rpm, consider giving it a good 10-15 minute run at full throttle and see what happens, then PM me.

If you worry about giving your engine a few revs, ask a diesel engineer, who will probably tell you that diesels like hard work. In Hallberg-Rassy's manuals they actually say "......More engines are damaged by slow running and by rust caused from poor winterising at lay up than overloading or due to many operating hours."

If I am the only person with a Yanmar 3YM30 that persistently overheats I will have to find an answer myself. I think however this may not be the case.

Of course if you have a solution, please PM me - but don't just suggest I change the impeller! I've changed a lot more than that!

 

[mcanderson]

I have a 3YM20 and was once warned about the build up of carbon I the exhaust elbow creating issues where the water joins in.

I can't be more specific. Sorry.

 

[parbuckle]

Some of the more welcome suggestions are the ones that cost no money and maybe you have not tried any of these.

Measure the volume of exhaust water at say 1500 and 3000 revs possibly using a clear 25 litre drum and check the timed amounts are correct.This might show up any restriction in flow.

Substitute temporary clear plastic hoses from seacock to raw water pump and observe the flow at high revs and maybe when underway.Some set ups can cause the pump to suck faster than the inlet will allow at high revs, small or restricted bore sizes will affect the efficiency of the pump at higher revs.

Another suspect is the exhaust water injection bend,the cast steel type are notorious for unseen corrosion,they look quite substantial but they can crumble like a biscuit inside and are difficult to see without removing and probing with a pointy thing.
Hope there is something here that helps.

 

[KAM]

I have a 3ym30. Whilst not experiencing an overheating problem I have had poor water pump performance. Last season it seemed reluctant to prime when starting cold. Engine has done 300 hours. Over the winter I dismantled the pump. Impeller was original and as new. The pump body looked as new and cam dimensions met specification. The cover plate was however badly corroded with deep pits. I suspect this was causing a poor seal. Refacing the cover plate seems to have cured the problem. I suspect the cover plate material is a poor quality brass it certainly seems to be different from the body casting. Whilst this may not explain your problem I think it highlights a quality issue with the pump which may affect other users. I never experienced this problem on my previous engine over 15 years usage.

 

[Blueboatman]

Parbuckles advice bang on IMO.
As a non marine engineer may I suggest that you verify that the engine will still give full revs under load( wasn't quite sure if you'd implied that it does in your post). With a clean hull n prop then If not, that is, to me, one of the very first indications of exhaust elbow partial blockage which would allow water and gas thru but still retain excess heat In the upper cylinders...
Secondly do you have say a galley seawater tap Tee'd into the water inlet plumbing? If that were sucking air a bit...
And do you have a calorifier fitted? If all else fails to reveal something, might be tempting to undo the in and out from the engine and fit a short, direct tube
accross thus verifying if it is in fact a restriction on the calorifier fresh water circulation side...
And lastly, we assume that the correct inlet and strainer have been fitted, are not cracked and the inlet is not fitted incorrectly too high in the boat( v unlikely on a production boat one would think),

 

[CJU]

I too experienced overheating on my 3YM at revs over 2,500, mid channel, which was a bit worrying. Anyway after 10 mins I restarted it and it was OK as long as the revs were kept low enough.
I put up with this until the end of season lift when I checked the: thermostat, temperature sender, kinks in pipes, impellor, exhaust elbow, blockages in saildrive leg, seacock, silt in the end caps.
When we relaunched and tested the engine the problem still existed, so in desperation I removed the heat exchanger core and found it was clogged with a slimy sludge, obviously restricting the amount of heat that could be absorbed by the tubes. I cleaned this off and refitted the core and it has been fine ever since (18 months).
I can only assume it was something to do with the engine coolant, although it has been changed every 2 years, as required, using the Yanmar brand. Also there doesn't seem to be any oil in the coolant, so maybe it was some residue from the manufacturing process, certainly the dealer didn't seem surprised when I mentioned it when buying new O rings.

 

[jwilson]

I have a 3YM20 and was once warned about the build up of carbon I the exhaust elbow creating issues where the water joins in.

I can't be more specific. Sorry.

New exhaust elbow. Still overheats.

 

[jwilson]

I have a 3ym30. Whilst not experiencing an overheating problem I have had poor water pump performance. Last season it seemed reluctant to prime when starting cold. Engine has done 300 hours. Over the winter I dismantled the pump. Impeller was original and as new. The pump body looked as new and cam dimensions met specification. The cover plate was however badly corroded with deep pits. I suspect this was causing a poor seal. Refacing the cover plate seems to have cured the problem. I suspect the cover plate material is a poor quality brass it certainly seems to be different from the body casting. Whilst this may not explain your problem I think it highlights a quality issue with the pump which may affect other users. I never experienced this problem on my previous engine over 15 years usage.

Had a complete brand new pump on last week - no different - still overheated.

 

[jwilson]

Some of the more welcome suggestions are the ones that cost no money and maybe you have not tried any of these.

Measure the volume of exhaust water at say 1500 and 3000 revs possibly using a clear 25 litre drum and check the timed amounts are correct.This might show up any restriction in flow.

Substitute temporary clear plastic hoses from seacock to raw water pump and observe the flow at high revs and maybe when underway.Some set ups can cause the pump to suck faster than the inlet will allow at high revs, small or restricted bore sizes will affect the efficiency of the pump at higher revs.

Another suspect is the exhaust water injection bend,the cast steel type are notorious for unseen corrosion,they look quite substantial but they can crumble like a biscuit inside and are difficult to see without removing and probing with a pointy thing.
Hope there is something here that helps.

My problem is I cannot replicate the problem except under way and under load, but now every single time you motor hard under way it overheats. I am beginning to suspect the diameter of the inlet piping, though it is as fitted and when near new the engine did not overheat. Lots of water flowing though, actually collecting it from the exhaust to measure could be tricky.

 

[jwilson]

Parbuckles advice bang on IMO.
As a non marine engineer may I suggest that you verify that the engine will still give full revs under load( wasn't quite sure if you'd implied that it does in your post). With a clean hull n prop then If not, that is, to me, one of the very first indications of exhaust elbow partial blockage which would allow water and gas thru but still retain excess heat In the upper cylinders...
Secondly do you have say a galley seawater tap Tee'd into the water inlet plumbing? If that were sucking air a bit...
And do you have a calorifier fitted? If all else fails to reveal something, might be tempting to undo the in and out from the engine and fit a short, direct tube
accross thus verifying if it is in fact a restriction on the calorifier fresh water circulation side...
And lastly, we assume that the correct inlet and strainer have been fitted, are not cracked and the inlet is not fitted incorrectly too high in the boat( v unlikely on a production boat one would think),

Thanks to everyone for suggestions.

Yes, with clean hull and clean prop (ie as now not long relaunched) I can achieve 3400 rpm at genuine 7.8 knots, but the engine will overheat in 5-10 minutes. Used to be it would only overheat occasionally, now it does it every time it is driven fairly hard.

No tee into inlet piping, and inlet deep underwater, pipe to Vetus strainer, then to engine.

There is a calorifier, on a fairly long pipe run. Does ALL the engine cooling freshwater go though this - I don't think so but am not an engineer? Worth trying a bypass pipe.

 

[Blueboatman]

CJUs suggestion to really look through the heat exchanger pipes sounds so likely....
If say the pink and blue antifreeze types had been inadvertently mixed at some stage.. Would they sludge up I wonder?( not an engineer).

I read of a mystery overheat in a Rustler42 in one of the back issues of the owners mag that defeated everyone....
Turned out to be a marine 'growth' in the plumbing AFTER the strainer and rubber hose..just thought it be silly not to mention that. Do a blow through with the dinghy pump perhaps to get a 'feel' for the current back pressure resistance?
Good luck and pls report back for all those hapless ones that come along in the future scouring the archives...

 

[vyv_cox]

The calorifier suggestion is a red herring. Once the fresh water in it is up to temperature the coolant will behave as if it doesn't exist. Prior to that it is extracting heat, although not a lot, from the coolant.

I would look at the CJU suggestion. You have checked the raw water side of the exchanger but the coolant side could well be fouled with something. The fact that the overheating occurs with the thermostat removed suggests something wrong in a big way and a faulty exchanger is one possibility

 

[misterg]

My problem is I cannot replicate the problem except under way and under load

That implies you don't get the problem running the engine under load with the boat tied up?

If so, it might be that the sea water pickup is badly sited with some sort of hydrodynamic effect causing reduced cooling water flow when under way (reduced pressure area, ventilation, etc.). Do you have a 'tear drop' shaped strainer over the water inlet? (Old chestnut alert: ) Which way is it pointing?

You could transfer the inlet pipe to another through hull (e.g. heads inlet??) temporarily to rule this out.

0.02p

Andy

 

[Rick James]

I have a SO35 with the same issue. I have sent you a PM

Rick

 

[Karyotakis]

I am experiencing the same problems with my 3YM30 Yanmar motor and I am interested to know if there is a conclusion to all above.
Yannis

 

[Joljaz]

Since near new my Yanmar 3YM30 in a Sun Odyssey 35 has occasionally overheated at high revs. It was an early build engine and has had the later larger heat exchanger fitted under warranty.

The power range at which this overheating occurs is steadily increasing. At first it was only 3000 rpm plus that would cause it (max revs are 3400) and the boat will reach this revs giving about 7.8 knots, so is probably not overpropped. Now it is consistently overheating after a period at 2900 and on one occasion after an hour at 2500. It's not just the alarm, the engine is overheating.

As I regard cruising revs to be 2400-2900 - if the engine is on it's because you want to get somewhere - this is unacceptable. This rev range translates to around 5 - 6.5 knots.

In the last ten days with the assistance of a Yanmar service agent engineer I have had a complete new raw water pump fitted, a new temperature sensor, and the heat exchanger insides look clean. Also tested the engine with the thermostat removed. Still overheats given high power running, though lots of water is clearly circulating and coming out of the exhaust.

I suspect that others with this engine have the same problem but may not know it, as they rarely run their engines hard enough.

The engine manufacturers UK distributors told me at last years Southampton Boat Show that they do not know of any overheating problems with this engine. As they paid for the heat exchanger to be changed on mine and at least two others I know of, this is obviously not true, but they stuck to their story that no-one else had a problem.

If you have a 3YM30 that overheats, please PM me.

If you have a 3YM30 that has never overheated, but only ever run at 1800-2500 rpm, consider giving it a good 10-15 minute run at full throttle and see what happens, then PM me.

If you worry about giving your engine a few revs, ask a diesel engineer, who will probably tell you that diesels like hard work. In Hallberg-Rassy's manuals they actually say "......More engines are damaged by slow running and by rust caused from poor winterising at lay up than overloading or due to many operating hours."

If I am the only person with a Yanmar 3YM30 that persistently overheats I will have to find an answer myself. I think however this may not be the case.

Of course if you have a solution, please PM me - but don't just suggest I change the impeller! I've changed a lot more than that!

I

Since near new my Yanmar 3YM30 in a Sun Odyssey 35 has occasionally overheated at high revs. It was an early build engine and has had the later larger heat exchanger fitted under warranty.

The power range at which this overheating occurs is steadily increasing. At first it was only 3000 rpm plus that would cause it (max revs are 3400) and the boat will reach this revs giving about 7.8 knots, so is probably not overpropped. Now it is consistently overheating after a period at 2900 and on one occasion after an hour at 2500. It's not just the alarm, the engine is overheating.

As I regard cruising revs to be 2400-2900 - if the engine is on it's because you want to get somewhere - this is unacceptable. This rev range translates to around 5 - 6.5 knots.

In the last ten days with the assistance of a Yanmar service agent engineer I have had a complete new raw water pump fitted, a new temperature sensor, and the heat exchanger insides look clean. Also tested the engine with the thermostat removed. Still overheats given high power running, though lots of water is clearly circulating and coming out of the exhaust.

I suspect that others with this engine have the same problem but may not know it, as they rarely run their engines hard enough.

The engine manufacturers UK distributors told me at last years Southampton Boat Show that they do not know of any overheating problems with this engine. As they paid for the heat exchanger to be changed on mine and at least two others I know of, this is obviously not true, but they stuck to their story that no-one else had a problem.

If you have a 3YM30 that overheats, please PM me.

If you have a 3YM30 that has never overheated, but only ever run at 1800-2500 rpm, consider giving it a good 10-15 minute run at full throttle and see what happens, then PM me.

If you worry about giving your engine a few revs, ask a diesel engineer, who will probably tell you that diesels like hard work. In Hallberg-Rassy's manuals they actually say "......More engines are damaged by slow running and by rust caused from poor winterising at lay up than overloading or due to many operating hours."

If I am the only person with a Yanmar 3YM30 that persistently overheats I will have to find an answer myself. I think however this may not be the case.

Of course if you have a solution, please PM me - but don't just suggest I change the impeller! I've changed a lot more than that!

 

[Joljaz]

Any new info on this problem? I have a 2004 SO35, this is my 4th summer on a cool Lake Michigan, never had a problem till this year. I normally run it at 2600-2750. Now overheats at 2600. Engine just turned 500 hours. All the usual checks turned up nothing,

 

[Slowboat35]

If the water flow via the exhaust looks substantial that is unlikely to be the problem. If it wasn't sufficient to carry away enough heat it would be a thin stream, near boiling and steaming - quite obvious.
I've had restricted salt water flow due to barnacles in the seacock and weed in the strainer as well as the usual mechanical reasons.

How hot is the exhaust elbow to touch? It should be not much more than warm where the 2"rubber exhaust hose joins it if seawater flow is sufficient. Hot hot elbow suggests restricted seawater flow.
Cool elbow (with engine overheating) points to inefficient heat transfer in the heat exchanger matrix which is by far the most likely place the heat isn't escaping anyway. Take the matrix out and clean it. Penny to a pinch of snuff it's full of crud, most likely on the fresh water side. Gentle use of a pressure washer followed by kettle descaler is a good start.
A failing fresh water pump will have similar effect even with a good matrix because the water isn't circulating properly. So check it.
The matrix is the only place where heat can get out of the engine - hot exhaust water = restricted cooling flow. Cool exhaust water indicates a problem within the matrix or the fresh water circulation. There really can't be anything else (let's not get into slipped injector timing - vanishingly unlikely) until the all too fallible heat exchangers have been eliminated.

Assuming exhaust water is OK then crudded up matix or failed freshwater pump are about the only options.

 

[Halo]

I had this problem. I have the bigger heat exchanger. The problem went away after I did two things
1. Replaced the raw water seacock. It fits on the sail drive and I exchanged the original with a stainless ball valve
2. Dismantled and cleaned the heat exchanger stack. This looked clean but I did get some carp out of it.

Are you sure the inlet pipe isn’t collapsing when you run higher revs. In a multi layer pipe it could be an inner membrane doing this. Is it a hose designed for suction ? If it is collapsing with the suction it will be reducing flow and could be the cause

I run my engine flat out for 15 minutes every few months.

 

[jwilson]

To Joljaz on Lake Michigan. It is quite possible your engine was an eary one with the smaller heat exchanger, and the problem never arose because of generally low water temperature. The first Yanmar 3YM users to report this were in Florida. UK Yanmar agents did not initially know about the problem, and did not pro-actively retrofit new and better heat exchangers, so many lightly used early 3YM engines with owners who never run them hard may still have the original heat exchangers.

Lots of good suggestions on this thread, but irst check if your engine is one of the early ones, serial number under about 5,000, Yanmar agents know the eaact engine number and should be able to identify your heat exchanger.