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Mike Banks · 25-03-2019, 14:39

It sounds as though the bypass is too big and the thermostat never gets to work at all--and the only way you can fix it is by modifying the system. I think that is the problem--as you yourself have discovered and it is one that has come up here before. A cold diesel is not a happy diesel as you have stated. 180 degrees Fahrenheit is the temperature at which my tractors seemed happy. But then--have you tested the thermometers by putting them in a glass Pyrex vessel and heating them up with a thermometer in there too so that you can see the temperature at which the thermostat opens? Might be worth a shot. It should be stamped on the thermostat itself--just to make sure.

Mike Banks · 25-03-2019, 14:44

Only an air cooled diesel should run hot. Air cooled engines often have to run hot in warmer climes to get enough temperature difference to cool efficiently.

I think Rolls Royce worked out that the ideal cylinder temperature for an IC engine was around 180 degrees Fahrenheit plus or minus a degree or two.

**a64pilot** · 25-03-2019, 14:45

Don’t do anything until you verify the temp range of the thermostat.
There are two temps of course, the cracking open and the fully open.

I’m betting your thermostat is a 160’ish thermostat, just like the majority of us have.

My Yanmar runs right at 160ish

TFM · 25-03-2019, 14:48

A general note: I bought the engine from Westerbeke in 2013 and picked it up at the factory in Fall River (or Taunton?) Massachusetts on a Saturday when production was shut down. I got a full tour of their production line from one of the supervisors. It was explained to me that the small boat diesels are stock tractor engines made by Mitsubishi, stripped of their unnecessary auto parts and fitted with marine parts customized by the company. I had owned Mitsubishi TV's and a van with their engine and felt they were quality items, so was pleased to now have one for my boat.

Marc1 · 25-03-2019, 15:05

Yes, I could do the test with the old thermostat since the new one is behaving in exactly the same way.
To answer TFM post, I believe you have air in the coolant. When I replaced the thermostat in the Nanni, I put coolant through the cap as you do in a car, yet the engine is not sitting horizontal but at some 15 or more degree and the thermostat housing is the highest point, so I had a massive air bubble in the system. The result was the fresh water pump cavitating and the engine temperature alarm going off. i realised my rookie mistake when I saw a sticker that reads "Coolant" under a brass cap on top of the housing. Then I also realised why the boat has a coolant container with a thin funnel that fits right in the 1/2" opening.
Things we do.
64, When I mentioned the thermostat not shutting off the coolant circulation as opposed to a tractor system ... the two systems are different. The tractor does not have raw water but air flowing to cool the coolant, and when you can block the air from circulating to get some heat in the tractor when it is cold, one can not close the raw water intake because the water pump">raw water pump is not designed to run dry. I suppose that some systems could have a diversion for the raw water to achieve this.

The Nanni achieves this by partial circulation of coolant to keep cooling the manifold and then opening the coolant to run through the heat exchanger when things get hotter.
Clearly this method is a compromise and fails towards the less of two evil. Yes, running cold is no good, and diesel likes to be loaded. But then don't cry if you overheat when loading it. It is a tragedy that such a good engine has such poorly designed marinization.

I wonder fi the keel cooling version is any better. Not that it would suit me, not interested in having a hot stack in the cabin but it would make much more sense.

PS
Weird, I keep getting this autocorrect ... water pump">raw water pump ... when I type raw water pump.

**Jim Cate** · 25-03-2019, 15:06

FWIW: Our Nnni 43 hp, based on Kubota V-1903, thermostat is marked "82" and runs at 80-82 deg C (180 F) unless in very cold seawater and low load, when it may drop a few degrees. Engine built in 1989, ~5000 hours.

Jim

FPNC · 27-03-2019, 14:14

Your way over powered. Factory spec on the thermostat is: Starts to open at 157 - 161 deg F, fully open at 185 deg F. Your engine is lightly loaded and the thermostat is doing what it is designed to do. Run your boat, enjoy your boat. Open it up every once in a while but do not worry about it.

Compass790 · 27-03-2019, 16:24

Lotta good replies here,
Get a workshop manual, that should tell you what thermostat should be. I'd try the vicprop calc to see what your prop should be. Agree with the overpowered idea for displacement mode, hard to get diesels warm with insufficient load.
Sounds like yr thermostat is working exactly as designed given what happened when you tried to build a bigger wave.
Lastly I wouldn't sweat it too much as raw water cooled diesels run a lot cooler & last for decades e.g our thermostat opens @ 42oC & fully open @ 52oC.
Having said that obviously better if it runs at design temp.

Marc1 · 29-03-2019, 16:35

Agree with all you guys are saying, but I am disappointed at the reply I got from Nanni Diesel Australia when I asked if they could supply an 80-82 C Thermostat

Quote:

Hi Marc,

Thank for your email. Frustrating that installing a new thermostat didn’t give you your desired outcome. The thermostat supplied to you from Collins Marine was originally supplied by Nanni Europe. Nanni are not in the business of designing and making Thermostats so i'm not sure information from the cruiser forum can be taken seriously when they refer to ‘Nanni Thermostats’. When the engine is built a specifically purchased 3rd party thermostat is installed. There can be variations which Nanni use for different reasons, however in 18 years of importing and selling these products I have not seen one with markings as you describe.

The temperature can vary through the engine rpm range, especially not long after start-up. There are different factors which can cause the unit to run cooler so if your thermostat is opening and closing as it should then you may need to look elsewhere. You can test your thermostat using heat to see if it is working as required.

If you are concerned with your engine’s performance I can recommend a marine engineer to inspect it.

Best Regards ... etc

Well ... did not expect a better reply but had to try.
From my experience with large diesel generators, I must say that a diesel engine even with no load can run at minimum temperature. That is what the thermostat is for. if temperature in an engine is the function of load, then there is no need for thermostat. Run at idle cold, temperature comes up as you increase the load. Not a good proposition.

The engine should be able to run at 80-82 C (180 Fancygrade ) after a warming up period with a wide range of loads. It is only when overloaded for a long time that the cooling system becomes insufficient in eliminating the excess heat and the engine overheats.
if idling for a long period, the temperature should not fall at all.

Marc1 · 29-03-2019, 16:50

Quote:

Originally Posted by Compass790

Lotta good replies here,
Get a workshop manual, that should tell you what thermostat should be. I'd try the vicprop calc to see what your prop should be. Agree with the overpowered idea for displacement mode, hard to get diesels warm with insufficient load.
Sounds like yr thermostat is working exactly as designed given what happened when you tried to build a bigger wave.
Lastly I wouldn't sweat it too much as raw water cooled diesels run a lot cooler & last for decades e.g our thermostat opens @ 42oC & fully open @ 52oC.
Having said that obviously better if it runs at design temp.

Yes, Compass, I have the workshop manual and ordered original part from Nanni ... to no avail.
Prop ... could probably do with slightly more pitch due to the fact that I have surplus power. The revs test, that is running the engine at WOT tells me the prop is correct since the engine run at 2800 rpm exactly what it's maximum revs is supposed to be.

Since i would never run the engine at wot because it achieves nothing, it may be that increasing the load by increasing the pitch will deliver some extra load at lower revs giving some fuel efficiency (no interested since it burns 4L / hour) and perhaps a better burn. A bit like using an overdrive in a truck.
Running like this will eventually mean having to decarbonize the engine for sure.

Was thinking in restricting the flow or raw water to the heat exchanger but decided against it. Too risky. A manually operated thermostat is prone to human error.
By the by ... this engine is fresh water cooled not raw water cooled ... well it is raw water cooled indirectly i suppose

Mirage35 · 29-03-2019, 17:14

I'm just jealous that you all seem to have sources for Nanni spares. After a year and a half trying, I just drove a five hour round trip to meet another "distributor" who in theory now has them on order for me. Couldn't get them out of him over the phone, but it seemed promising in person. Maybe there's still hope.

OT I know, but needed to vent.

Compass790 · 29-03-2019, 17:25

Quote:

Originally Posted by Marc1

Yes, Compass, I have the workshop manual and ordered original part from Nanni ... to no avail.
Prop ... could probably do with slightly more pitch due to the fact that I have surplus power. The revs test, that is running the engine at WOT tells me the prop is correct since the engine run at 2800 rpm exactly what it's maximum revs is supposed to be.

Since i would never run the engine at wot because it achieves nothing, it may be that increasing the load by increasing the pitch will deliver some extra load at lower revs giving some fuel efficiency (no interested since it burns 4L / hour) and perhaps a better burn. A bit like using an overdrive in a truck.
Running like this will eventually mean having to decarbonize the engine for sure.

Was thinking in restricting the flow or raw water to the heat exchanger but decided against it. Too risky. A manually operated thermostat is prone to human error.
By the by ... this engine is fresh water cooled not raw water cooled ... well it is raw water cooled indirectly i suppose

I realise yr engine is fresh water cooled. All I was trying to get across is that the engine can, like a raw water cooled engine, run cool for a very long time but it's not ideal.
The other thing you could try is modifying another thermostat with yr desired temp setting to fit yr engine. Shouldnt be hard to do.Good luck with it

Vila · 18-09-2022, 07:03

I have a Nanni N4.50 in my Cabo Rico 38 and the engine operating temperature is 70c. 70c equals 158 F and this is the normal operating temp for the Nanni N4.50. As you may know the thermostat on the engine is located in the center of the heat exchanger along the left side of the engine.

When my engine was first installed, they did not connect the hot water properly and the temp would climb until the engine would overheat. After emailing Nanni directly I discovered there are special installation consideration if your hot water heater is higher than the engine like mine. There is a note about this in the Nanni installation manual, but they do not provide any details for the installation.

The heater water flow for this situation should go from the engine to the water heater. From the water heater it needs to then go to an expansion tank with a 4 psi cap and the tank must be higher than the water heater. From the expansion tank the flow goes back to the engine.

In my engine photo, I am pointing to the hose that goes directly to the water heater. For the expansion tank photo, The hose from hot water heater connects to the tank input on the left side of the tank. The exit hose at the bottom of the tank then goes back to the engine. After completing this installation, I ran the engine with the expansion tank cap off and had to add coolant to the tank several time until all the air bleed out of the coolant circuit.

For some reason my photos appear sideways.

Miket99 · 22-10-2022, 15:58

Quote:

Originally Posted by AnglaisInHull

I'm just jealous that you all seem to have sources for Nanni spares. After a year and a half trying, I just drove a five hour round trip to meet another "distributor" who in theory now has them on order for me. Couldn't get them out of him over the phone, but it seemed promising in person. Maybe there's still hope.

OT I know, but needed to vent.

Did anyone find a USA source for Nanni spares? Or Kubota parts that will work? Miket99