Turbo vs normally aspirated

[a64pilot]

Usually when a turbo goes, the engine won't make enough power to pull the hat off your head to use a farmer term, but it will smoke like the devil.

[sardinebreath]

In looking at a used engine with several thousand hours, is it any more or less difficult to identify a TD that has been run badly and therefore likely to be a maintainance nightmare than it is an NAD? Would a comprehensive engine survey be significantly more expensive on a TD?

[socaldmax]

Originally Posted by a64pilot

socal, how do you like your Duramax? I've had mine since new in 2001, did have to do the injectors and that was a whole lot more work and expense that it should have been, but other than that I love it. I really get 17 MPG in a one ton dooley, love the turbo.

When mine runs, it runs great, but I must have gotten a lemon, built on Monday or something. I've gone through 2 engines, 2 sets of injectors, 1 injection pump, 1 fuel pressure regulator, and now I need all 8 injectors replaced again. All of the major problems revolve around the injectors, and I have a 3 stage filter system with a lift pump! I pump it through a 30 micron filter/water separator, a 10 micron filter, then the stock filter. I use additives, I buy clean fuel, it makes no difference.

My next truck is going to be either an '08 Duramax, or if I can't get a great deal on one, I'm thinking about a used class 8 truck, like a Freightliner or Volvo. With my trailer, I'd get about the same fuel economy with a lot more safety margin for probably the same price as an '08 Duramax.

[bstreep]

I'm not going to read all of the responses. Just my opinion, as an owner of a 75hp Yanmar Turbo (4JHDTBE):

Turbos do NOT belong on sailboats. EVER. I try to be good about running them hard, but let's face it. In and out of the slip, they idle. So they run for 20 minutes at idle when cold, and 20 minutes at idle when shutting them down. Yanmar recommends a "turbo wash" WEEKLY. The turbo is a huge pain in the a$$ to pull out (I'm down to about 2 hours in, 2 hours out). Be forewarned.

[Paul Annapolis]

I've been on boats with turbos a few times but am definitely no authority...heck. I am not much of a mechanic BUT... I like their performance and added efficiency. I have been on plenty of naturals and a few turbos and I like the sound and the extra power and efficiency. I was just on a back Cove 37-a remarkable ad finely crafted boat and it had a 500 hp Yanmar with a turbo. At about 1200 or 133 or so it just kicked in going from a loud thumbing engine noise to a smooth Turbo whistle. Talk to mechanics and see what they say.

[Horror Hotel]

As the old muscle car saying goes "there's no replacement for displacement". Some of this turbo advice is spot on, much of it is just personal experience. "I had a turbo it was trouble free for the life of the engine " or "my turbo was a maintenance nightmare". For a sailboat engine under 80 hp or so, it's just not a great advantage , there is no free lunch. Force induction does give a better cylinder fill but power comes from burning more fuel. Making 60 hp requires the same fuel whether NA or turbo. Sailboats go so slow that it's pointless to talk about the boost power band and engines running smoother. All motors run smoother at increased RPM, adding boost doesn't smooth anything out.
Turbo prices can be all over as well, if it's a kubota and millions of tractors were made it could be way cheaper than a 20 year old limited production Volvo. Turbos also fail in many ways. Oil seals, shaft beatings, it could still make boost but be leaking oil to either side of the turbine. If the intake side you burn it with cloud resulting, if the exhaust side it might smoke way less. It's just another failure point that can be avoided by not having one. Add to this the inter-cooler could also fail in a few ways and you wouldn't have a inter cooler without a turbo plus it's associated feed/ return oil lines. Some of the higher performance turbos also have coolant feed/return lines to cool the turbine core. Turbos run hotter because they burn more fuel than the same block with as NA. More power from more fuel, more fuel burn = more heat. A slightly more taxed cooling system.

It's not the same as cars but key parts of the technology are the same. As far as the Duramax issues my experiences with the Chevy Duramax is that the yard a very poor motor, but the die hard Chevy guys put up with it rather-than drive a ford.

[sardinebreath]

Originally Posted by bstreep

I'm not going to read all of the responses. Just my opinion, as an owner of a 75hp Yanmar Turbo (4JHDTBE):

Turbos do NOT belong on sailboats. EVER. I try to be good about running them hard, but let's face it. In and out of the slip, they idle. So they run for 20 minutes at idle when cold, and 20 minutes at idle when shutting them down. Yanmar recommends a "turbo wash" WEEKLY. The turbo is a huge pain in the a$$ to pull out (I'm down to about 2 hours in, 2 hours out). Be forewarned.

That's been my gut feeling but I wanted to hear it from an owner. I think it helps me cross one boat off the list. How do you like your Mc 47---other than the engine?

[Horror Hotel]

If the boats nice why can't you lower your offer to reflect a repower. Passing on a nice boat because of a turbo is a little extreme. Is there no wiggle room with that boat? I'm slightly biased, I think all boats need new engines. If its 15 years or so and you plan to cruise far and wide, save the hassles and re power now. Especially when you could use it as a negotiation issue. My guess is if dealing with boats under 50k you can't work the new engine angle to well, but a boat listed at 80k+ you could say you love the boat but don't trust the engine take 15k off and it's a deal. My buying advice is to make many offers quick, rather than falling in love with each one and spending 30 days dealing only to have it not work. Buy the turbo boat but have your offer reflect that you really hate turbos.

[markpierce]

Eighty horsepower, sans turbo, is quite sufficient for me. Besides, don't need the extra complication.

[socaldmax]

Originally Posted by Horror Hotel

As the old muscle car saying goes "there's no replacement for displacement".

That may have been a popular saying back when my grandfather raced, but it's hogwash now. A 442ci twin turbo RHS small block will make 1400 hp at the rear wheels. A 600ci Brodeck big block tops out at 1,000 hp. There most definitely is a replacement for displacement, it's called boost.

Some of this turbo advice is spot on, much of it is just personal experience. "I had a turbo it was trouble free for the life of the engine " or "my turbo was a maintenance nightmare". For a sailboat engine under 80 hp or so, it's just not a great advantage , there is no free lunch.

Agreed.

Force induction does give a better cylinder fill but power comes from burning more fuel. Making 60 hp requires the same fuel whether NA or turbo. Sailboats go so slow that it's pointless to talk about the boost power band and engines running smoother. All motors run smoother at increased RPM, adding boost doesn't smooth anything out.

Disagree. I own both, and the turbo engine is much smoother, more efficient, and does get significantly smoother once boost rises above 7 psi or so. Diesel engines are essentially air pumps, and turbos make them far more efficient. Power is a function of the amount of air moved in conjunction with fuel burned. Take an 80 hp NA diesel and a 100hp TD and run them both on a load requiring 60hp and the TD will consume less fuel AND have lower EGTs.

Turbo prices can be all over as well, if it's a kubota and millions of tractors were made it could be way cheaper than a 20 year old limited production Volvo. Turbos also fail in many ways. Oil seals, shaft beatings, it could still make boost but be leaking oil to either side of the turbine. If the intake side you burn it with cloud resulting, if the exhaust side it might smoke way less. It's just another failure point that can be avoided by not having one. Add to this the inter-cooler could also fail in a few ways and you wouldn't have a inter cooler without a turbo plus it's associated feed/ return oil lines. Some of the higher performance turbos also have coolant feed/return lines to cool the turbine core. Turbos run hotter because they burn more fuel than the same block with as NA. More power from more fuel, more fuel burn = more heat. A slightly more taxed cooling system.

Nope, again, more boost equals cooler EGTs and less engine heat. Yes, there is an added heat load on the oil from the turbo itself, but the cylinders and engine run slightly cooler. With a properly sized cooling system, it's not like there isn't a huge amount of coolant available. I do agree, a turbo does add a bit more complexity, but it's worth it to some people. If you like simplicity, remove the engine and get some oars.


It's not the same as cars but key parts of the technology are the same. As far as the Duramax issues my experiences with the Chevy Duramax is that the yard a very poor motor, but the die hard Chevy guys put up with it rather-than drive a ford.

The Duramax engine itself is one of the most advanced diesel engines ever designed. Unfortunately, the injection system and the problematic injectors were designed by Bosch. Ford, on the other hand, was at one point buying back defective 6.0L trucks faster than they were selling them. LOL

You can verify all of that if you like.

[Horror Hotel]

I have no interest in debating you word for word. Some of what you claim is relevant, some is not. It just doesn't seem necessary to turbo a small sailboat engine. Frankly my whole opinion changes once we start talking about making serious power, in larger boats with high HP. But. 80hp and under it's not needed.
I can't find any reference to turbos having lower EGTs while under loads and making boost. Turbos act as a heat sink and tend to produce more heat while making more power.

[valhalla360]

Originally Posted by Horror Hotel

I have no interest in debating you word for word. Some of what you claim is relevant, some is not. It just doesn't seem necessary to turbo a small sailboat engine. Frankly my whole opinion changes once we start talking about making serious power, in larger boats with high HP. But. 80hp and under it's not needed.
I can't find any reference to turbos having lower EGTs while under loads and making boost. Turbos act as a heat sink and tend to produce more heat while making more power.

I suspect there is a kernel of truth in the lower EGTs but in an apples to apples comparison its not true.

Let's say your boat needs a 40hp engine (let's assume this is truth and not get into how to determine the appropriate power which is a different debate):
- If you take the 40hp NA block and strap a turbo on it to get a 60hp engine but limit yourself to the power output equivalent to the 40hp NA version (ie: you never put out more than 40hp and cruise at the same speed), there may be a slight difference in EGTs as the turbo pumps additional cool air into the engine block. Probably not enough to make a significant difference but it should be slightly cooler.
- If you do an apples to apples comparison, you will compare a 40hp NA engine to a 40hp turbo with a smaller block. In this case, I seriously doubt it will run cooler. While the additional air intake will scavenge a bit of heat, you are concentrating roughly the same heat input into a smaller space.

[Horror Hotel]

Everywhere online I look seems to say EGTs will be higher on a turbo engine under load. Sure after the turbo the temps and exhaust gas velocity drop off as the turbo extracted the energy from it. Every performance turbo system I've dealt with has had heat as it's #1 enemy. Not that any of this matters, but all this "it's not hard on the engine" talk is in direct contradiction to the older, heavy, slow turning, long lasted diesels of the past.

I just repowered and the new diesel that weighs almost 200# less than the previous engine and is more powerful. I honestly believe that the older engine would have outlasted this new yanmar. But the costly repairs every 2 years and not knowing when or where I would be stranded makes the new engine a real stress relief.

[jtsailjt]

Originally Posted by bstreep

I'm not going to read all of the responses. Just my opinion, as an owner of a 75hp Yanmar Turbo (4JHDTBE):

Turbos do NOT belong on sailboats. EVER. I try to be good about running them hard, but let's face it. In and out of the slip, they idle. So they run for 20 minutes at idle when cold, and 20 minutes at idle when shutting them down. Yanmar recommends a "turbo wash" WEEKLY. The turbo is a huge pain in the a$$ to pull out (I'm down to about 2 hours in, 2 hours out). Be forewarned.

I'm a new owner of a remanufactured 88hp yanmar turbo diesel and the guidance I can find regarding frequency of turbo washing ranges from 150 to 600 hours. Does your manual really say weekly? Did you mean weekly if run 24 hours a day? What do other yanmar turbo owners say about how often they recommend turbo washing assuming normal use?

All diesels like to be run around 80% power for the majority of the time, nothing different about a turbo versus NA diesel there. Whether or not you have a NA or turbo diesel, you'll still be operating it at low power settings at startup and approaching the slip. But since having a NA engine will mean it's bigger than an equivalent HP turbo engine, you'll be running a bigger engine at lower power settings during this period.

As I mentioned earlier, I'm not experienced at running a turbo but it seems to me that at least a few minutes of low power warmup and warm down of the engine, during which nothing is being demanded of the turbo would be a good thing to allow for good lubrication and gradual warmup and to dissipate excess heat before shutdown. Am I wrong?

[socaldmax]

Originally Posted by Horror Hotel

I have no interest in debating you word for word. Some of what you claim is relevant, some is not. It just doesn't seem necessary to turbo a small sailboat engine. Frankly my whole opinion changes once we start talking about making serious power, in larger boats with high HP. But. 80hp and under it's not needed.
I can't find any reference to turbos having lower EGTs while under loads and making boost. Turbos act as a heat sink and tend to produce more heat while making more power.

I'm not interested in arguing either, just that some, only a small part, of what you said directly contradicts my experiences towing with a turbo diesel engine with a lot of instrumentation on it - 2 boost gauges, 2 EGT gauges, 2 coolant temp gauges, 2 trans temps gauges, 1 oil temp gauge, 1 differential temp gauge.

As you said, added fuel creates more power and heat, but adding more boost in conjunction creates even more power and slightly less heat.

I do agree with you, on a smaller engine on a boat it's probably not worth the added expense or complexity and that's really what this discussion is all about.


However, if VW ever decides to build a TDI marine engine with a super reliable sail drive, I think a lot of people would be willing to repower for that.