Yanmar engine choice

[SailRedemption]

Originally Posted by aluijten

Last boatshow I was in september this year the good people of Yanmar proudly presented the new line of diesels (common rails) starting at 45 HP.
Actually the sales person I talked to was very cautious about the common rail in combination with sail boats. The funny thing was that the same engine block without common rail delivered over 50 HP.

Oh wow, I figured it would have ore hp output since it's a computer controlled ignition timing.. I wonder if the 45 get a significantly better fuel consumption..

I haven't ran mine long enough to know consumption rates.

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[bstreep]

Ours has just under 3000 hours on it. Be careful with new diesel hp ratings. The better number to look at is torque. The common rail diesels should offer a substantial performance improvement.


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[Dockhead]

Originally Posted by SailRedemption

I have the Yanmar 4hj4-te 75hp turbo on my 47 mono.. Gets to hull speed and then some!

Don't listen to others that say turbos don't belong on boats, they have been in the marine industry for years. If they had problems it's because they don't know how to run a diesel engine properly. You can't lope around all the time, you have to get a load on it(like you already know) and get the temp and exhaust flow up. It doesn't have to be there all the time, but that's with any diesel engine. They are meant to be ran at a load. Most commercial fishermen use turbo diesels with thousands of hours on them because the run them like their supposed to.

I picked the Yanmar because it was the lightest, smallest of the bunch in that hp range. Had I more room and didn't mind the weight I would have gotten a non turbo Beta for sure. Not sure on price, both great engines though. If you have the money to swing get the 4jh4-te, it's non common rail and non after cooler (which I agree adds complexity and added maintenance).

Oh, qnd the turbo DOES sound sweet when it spools up! wink

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I agree with this.

I like turbos on boat engines and actually think that it's better to have a smaller displacement turbocharged engine compared to a larger displacement naturally aspirated one.

Why? Well as A64 said -- weight, which is especially crucial on cats.

But also because sailboat engines spend 95% of their lives putting out 20% of their maximum power. They will be better loaded if they are smaller, which is made possible with the turbo.

Turbocharging adds to efficiency, makes the engine quieter because the turbo absorbs the exhaust pulses, and makes it smoother.

There is no problem running modern turbo boat engines at low speed as long as you "blow them out" regularly -- as Yanmar tells you to do in the manual.

Turbochargers are extremely simple devices with approximately one moving part. I don't think that they add much complexity, and the benefits are very significant.


Now as I understood the OP, however, he is also asking about oversizing the engine in terms of total power. That's a different question. On a mono, I would definitely do it, and plan to have lots of engine power on my next boat (if I can ever afford to build it). But on a cat -- weight is death. I would think carefully about that.

And instead of overpropping, why not use a variable pitch prop -- a much better solution than overpropping with a fixed pitch prop. Unfortunately Hudested props are not made in those sizes (but my next boat will have one of these!) but you can use Brunton. Downside on a cat is that the Brunton Autoprops have more drag when feathered than normal feathering props, and cats have two, which doubles the harm. But rather than just overprop a fixed pitch prop I might still consider it.

[a64pilot]

There are one or two other advantages to turbos, they can actually decrease engine head and exhaust valve temp. See there is a period of valve overlap on an engine, it's when both valves are open, if you have a pressurized intake tract, air will flow through both valves more effectively savaging the combustion chamber of exhaust gas and blowing cooling air through, they are more efficient as they use the heat from the exhaust to drive them, this heat is normally lost energy, but a turbo harvests this heat.
You run into reliability problems sometimes when a turbo is used to greatly increase an engines HP, and this extra HP is used as it is of course then more stress on the engine.
There is a reason most all farm tractors and all OTR trucks etc all have turbos. Common rail and turbos go together like socks and shoes too, nothing is smoother, quieter and more powerful than a blown common rail engine.

Just have to decide for yourself if you want all that complexity on your boat. I believe I would on a Cat as I have a back-up, not so sure I would want that if I only had one though.

Different engines as they can be, but right now I'm trying to find an ECU for my Husqvarna motorcycle, it's electronic fuel injected, and runs far superior to a carborated one, but finding an ECU is proving to be hard,and I'm sure expensive, a carb I can take apart and clean, an ECU, well only thing there is to find a new one.
Same with the more complicated Diesels, ECU goes out, engine is down, there is no by-passing it.

[Dockhead]

Originally Posted by a64pilot

There are one or two other advantages to turbos, they can actually decrease engine head and exhaust valve temp. See there is a period of valve overlap on an engine, it's when both valves are open, if you have a pressurized intake tract, air will flow through both valves more effectively savaging the combustion chamber of exhaust gas and blowing cooling air through, they are more efficient as they use the heat from the exhaust to drive them, this heat is normally lost energy, but a turbo harvests this heat.
You run into reliability problems sometimes when a turbo is used to greatly increase an engines HP, and this extra HP is used as it is of course then more stress on the engine.
There is a reason most all farm tractors and all OTR trucks etc all have turbos. Common rail and turbos go together like socks and shoes too, nothing is smoother, quieter and more powerful than a blown common rail engine.

Just have to decide for yourself if you want all that complexity on your boat. I believe I would on a Cat as I have a back-up, not so sure I would want that if I only had one though.

Different engines as they can be, but right now I'm trying to find an ECU for my Husqvarna motorcycle, it's electronic fuel injected, and runs far superior to a carborated one, but finding an ECU is proving to be hard,and I'm sure expensive, a carb I can take apart and clean, an ECU, well only thing there is to find a new one.
Same with the more complicated Diesels, ECU goes out, engine is down, there is no by-passing it.

Common rail or not is a different question, from turbo or not.


Diesel engines work so well with turbos that I don't think non-turbo diesel engines are even made any more, outside of some marine engines. Certainly no such thing as a naturally aspirated diesel truck or car engine, and for decades by now. Its different from spark-ignited engines because there's no problem with detonation. There is no problem with stress from the extra power as long as the engine is designed for it. So say you want to design a 100 hp marine engine. You design the crank, bearings, rods, etc. for 100hp, you just do it in 2 liters of displacement rather than 4, if you go turbo.

Meanwhile that same engine works much better as a 20 horsepower engine at cruising speed. The 4 liter engine will be running very cold, putting out 20 horsepower and pumping 2 liters of air through on every revolution. The 2 liter turbo engine will only circulate 1 liter of air and will be better loaded.


As to common rail -- I don't know what to think about it. A64 has ably described the advantages. I have a friend who used to own a large Bosch fuel injection repair facility, and he swears that common rail is much more robust and reliable than mechanical. Maybe we need a few more years of experience with common rail yacht engines before we know whether they are reliable in practice, but I would be seriously tempted if I were buying a new engine today.

[aluijten]

Originally Posted by Dockhead

As to common rail -- I don't know what to think about it. A64 has ably described the advantages. I have a friend who used to own a large Bosch fuel injection repair facility, and he swears that common rail is much more robust and reliable than mechanical. Maybe we need a few more years of experience with common rail yacht engines before we know whether they are reliable in practice, but I would be seriously tempted if I were buying a new engine today.

I've been told the high pressure from common rail becomes extremely eroding at the injector nozzle when any water droplets are present. These droplets explosively vaporize when passing the tip of the nozzle. That process is much less of a problem at the relatively low pressure of conventional injection.
So as long as you use good and clean diesel all is well, but in the marine environment that may be different, especially on sailboats will little fuel turnover.

[a64pilot]

I brought up common rails as they go with Turbos so well, and speak to the added complication that you do get with a turbo.
Another thing about turbos is it's common for people to think HP adder as well Turbo Porsche and many other sports cars, but what turbos actually do very well is add torque, anybody that has ever dropped a plow into the ground of pulled a hill in a big truck knows what I'm talking about, do that and the turbo starts to whistle as boost build and up the hill you go, a normally aspirated engine, you down shift and turn lots of RPM to make the power.
So if you want say 50 HP from a 2 L engine a turbo may can get you there at 1800 RPM, where an NA engine will have to spin 2800 RPM.

Common rail typical fuel pressure is usually around 30,000 PSI or higher, early mechanical pumps were around 3,000, newer ones much higher. A MAJOR reason a Diesel is a relatively low RPM engine is the limited time you have to get the fuel in the combustion chamber, higher RPM of course less time, Higher pressures mean much more fuel in less time, jack up the fuel pressure and you can turn up the RPM.

But when you get up around 30,000 PSI, you essentially have a water jet, a tiny bit of abrasive will easily cut through steel and your injector nozzle, I don't think it's water actually but tiny bits of dirt that kill a common rail injector.

[a64pilot]

Oh, the weak link in my opinion of common rail is it's electric, requires a pretty sophisticated computer to determine injector timing, pulse width etc. Each injector is of course electrically fired and you wouldn't believe how much current it takes.
Mechanically it's much simpler than mechanical injection, all you have is a hydraulic pump that holds a constant high pressure, the magic is in the injectors
But a sophisticated engine computer and electrically operated injectors on a boat? I'd say carry a spare ECU at least, and hope you don't get a lighting strike.

[Bahia]

Hi guys,

I thank you very much for the input and food for thoughts that you have provided.
Definitely I will not go for the Common Rail engines, as I rather have a simple system.
The CR is a little too fragile and demanding. The saltwater and corrosion issues won't be in my favour I believe...

But I'm still not over the turbo'd engine yet.
I would need to find a cheap source for the engines and to compare the price tag difference and to have alook on my accounts...
However I am not a big fan of these autoprops as I see them as a potential source for failures.
I rather have a fixed prop that is cheaper and does not require any maintenance as such.
Regarding the size of the props I will probably have to do some extended calculations and to see what is the best option. Maybe I will just get the "standard" prop size and run only one engine at a time. If I need to speed things up, I can always power up the second one.
Running on one engine will increase lifetime (in overall for both engines) and I believe I shall not feel any disadvantages in fuel consumption due to drag, coz running one engine is more economic then producing same power from 2 engines.

Cheers
Bahia

[onthewateralot]

Turbos are great at boosting efficiency but remember it is another moving part to fail. Failures can occur mostly by the bearing seal going to heck which can happen on both the exhaust side or inlet side. Either way it happens very quick with huge amounts of oil going either into the engine (runaway engine since the oil acts as fuel) or out the exhaust. If your not quick and, I mean very quick, then you have either ruined your engine with an oil slick everywhere on the water (break out the dawn!) or your engine turns over very fast, getting so hot it glows ....and fiberglass likes to burn. Both ways it has happened to me but I recognized the problem and in the case of my tugboat (cummins engine) I used my hand to cover air inlet, but I knew what to recognize. Think you can act that fast if you can't get there fast enough?..........

[onthewateralot]

Also I would never have a diesel in my boat, whether it's for pleasure or work and I am a marine contractor, that has electronics on the engine. Electricity and water do not mix.....PERIOD. Again it is another part that will fail and all it takes is one wire, one circuit, one transistor or whatever and there you sit. In my case I'm sitting in the Bahamas right now with a junk British Lehman (2401 "York") engine trying to figure out a replacement. They actually put a rubber timing belt on the engine (which ran great up to now) and when belt broke it allowed piston to hit the valves......wait till I meet that engineer who designed it. In the meantime learn from my mistakes.........

[John Holbrook]

Is the turbo on the Yanmar 75hp producing full boost at 1800rpm?

Originally Posted by Bahia

Hi guys,

I'm looking to replace my engines & saildrives in my FP Bahia 46.
I've got the 40hp 3-cylinder bolted to SD31 drives now, however the boat had 4 cylinder engines before.

So my options are now again the 3-cylinder or the 4-cylinder with SD60 saildrives.
But also I'm a bit interested in the 4-cylinder turbo engine... since the difference in price is not that big.

I'm thinking to get the 75hp turbo and to overprop it.
My thoughts are to calculate the prop to take 30kw at 1800rpm engine speed.
This will be exactly 75% load (engine delivers max 40kw at 1800rpm).
In order to have cruising speed at around 1800rpm and max rev at around 2400rpm.

Is there anything wrong with my thoughts?
Share your opinion please.

Thanks
Bahia

[a64pilot]

Originally Posted by John Holbrook

Is the turbo on the Yanmar 75hp producing full boost at 1800rpm?

On every turbo engine I have ever had, that is more dependent on load than just RPM, meaning I believe it would depend a lot on displacement and how it's propped. Assuming 1800 RPM is half full RPM and the boat is propped to make full rated RPM, I doubt it will be on all that much boost, but then I don't know what full boost is, do you?
Boost will vary greatly by engine, my truck will make 23 lbs of boost in stock trim, my Miata about 5 or 6 I think.
I would bet the Yanmar at 1800 RPM would be less than half of full boost?

[Bahia]

Hi guys,

I actually had ordered the NA engines 4JH5E last year and am installing them right now.

Turbos would have been sweet if I was the only one using the boat. But since I am chartering it out and most of the time my skipper is using it... I rather have it failsafe...

Unfortunately it is not just plug & play as I have to raise the engine mount surface & extend it, too. I had the 3JH3E before.

Also the 3JH3E has a narrower footprint of the engine mounts. 25mm less on each side. But it looks like I can use the old mounting brackets. They bolt on on the new engine...



Same for the engine panels. The cutouts for the old panels are a bit wider than the new panels. So I had to come up with a solution...



Cheers

[dlymn]

We have a 4JH TE turbo and it performs well. Yanmar recommend running it at 2700 rpm for cruising and the WOT for 5 minutes every hour. This I think is to reduce cylinder glazing brought on by light load operation