Turbo vs normally aspirated

[Cheechako]

Some people have had good luck with Turbos, but there have been many a thread on here about Yanmar Turbo issues. Turbos work the engine harder, and often shorter life can result. I figure it this way, if you get a 50 hp non tubro engine the HP comes from true displacement, if you get a 50 HP turbo engine, the displacement is less (you're getting a smaller engine), and it is maxed out to produce the HP.

[valhalla360]

I wouldn't rule out a boat with turbos but I wouldn't seek it out.

A turbo works well on a road vehicle where you need short bursts of power for acceleration or climbing a hill (they are great for high altitutde running as the less dense air is compressed so there is almost no loss of compression). Then when cruising on level road, you need far less power.

Secondarily is weight consideration. In the small 20-50hp engine range, you aren't likely to save enough weight to really see a difference in fuel economy. Now if you are talking about a big planing power boat, you can save a lot of weight by pumping out more power from a smaller block with a turbo and it can make sense.

Non-planing cruising boat engines are normally sized based on the horsepoer needed for cruising at hull speed. That's a steady load on the engine and naturally aspirated is the way to go.

[Dockhead]

I have owned both turbo and non-turbo diesel engines.

My present boat has a Yanmar 4JH3HTE, 100 horsepower, turbo and seawater cooled intercooler.

There are pluses and minuses to both turbo and non-turbo.

Non-turbo obviously is simpler, and simple is a big plus at sea.

Turbo, however, has a number of advantages:

1. Same power from a smaller, lighter, more compact engine. Means you sail faster, and can get to the engine more easily.

2. Higher efficiency. Enhanced still more by the lighter weight.

3. Quieter and smoother -- the turbine absorbs the exhaust impulses; smaller and lighter engine has smaller reciprocating parts; the turbo evens out the difference in pressure between intake and exhaust. Comparing the 4JH3HTE to the massive 4.4 liter Perkins non-turbo engine in the Oyster I almost bought: The Perkins shakes the whole boat and makes a roar you can hardly hear over -- it sounds like a Russian tank engine. The Yanmar, on the other hand, makes a smooth, sweet, very quiet sound which hardly disturbs anyone -- so motoring is a pleasure.

I guess the biggest plus is smaller and lighter.

I have had some trouble with my Yanmar, but I don't think it's related to the fact that it's turbocharged.

All in all, I think I would go with a turbocharged engine again, if I ever buy another boat, and if I have a choice. Sometimes a little extra complexity is worth it, even on a boat. And as Dave said, turbo marine engines do not suffer from any particular problems which non-turbo engines are not subject to. The turbines themselves are very reliable.

[a64pilot]

Personally I like turbos, at least in Diesel applications, wouldn't give you two cents for one in an airplane though.
As long as you follow some simple turbo rules, like ALWAYS idle the engine for several minutes before shutdown to cool the center section or the oil will coke and your turbo will be toast as the coke eats the bearing, a loose bearing will allow the compressor to contact the housing, and then you need a new turbo. But prevention is easy, just keep the oil changed and idle for two or three minutes before shutdown.

As far as turbos being only for road engine the only occasionally use high power, try finding a N/A farm tractor, large generator, water pump, or even train for that matter, all those are run at high continuous power settings.

Now a turbo engine is meant to be run so to speak, it's not the best application for an engine that is used to charge batteries and only run for a couple of minutes to get into and out of a slip or anchorage etc.

[Cheechako]

Toyota builds pretty good cars. I had a Supra Bi Turbo for a while. The engine rings wore out at about 75k miles... due to the high turbo pressures. I guess I shoulda kept my foot out of it all the time....! That car was totally smoooth at 110 as it was at 35...

[valhalla360]

Originally Posted by a64pilot

As far as turbos being only for road engine the only occasionally use high power, try finding a N/A farm tractor, large generator, water pump, or even train for that matter, all those are run at high continuous power settings.

chorage etc.

And weight and size is a key factor in all of those. Not acceleration. Train engines are massive as it is. How much more massive would they be without the turbo.

Given the small sailboat engine application, I don't think you are going to save a noticable amount of weight. (assume, say a typical modern 40'er with a 30-40hp engine)

I'm not suggesting a diesel turbo is a bad engine just that all else being equal, I would lean towards a naturally aspirated engine for this application as the simplicity outweighs the potential savings.

[socaldmax]

Originally Posted by sardinebreath

Thanks for all the input, folks. I suppose that I wouldn't let a turbo dissuade me from a boat that I otherwise coveted but there doesn't seem to be much consensus about how much extra trouble/expense/risk a turbo might present and whether or not it's worth it. Again, if I was looking for reliability and maintenance economy, and basing my decision on what I know about gas engines, I wouldn't get near a turbo. I find it difficult to believe that a turbo diesel going to go as long between overhauls as an N/A, but the number of TDs utilized in commercial trucking makes me wonder about that.

You're hinting at the right answer when you consider that all commercial trucks are turbo diesel.

I own a NA Toyota corolla diesel and a Duramax turbo diesel. The turbo diesel burns far cleaner than the NA diesel, especially when the boost really gets up there. True, neither of them is in a marine environment, but any engine that burns cleaner is going to go longer between rebuilds (all else being equal) just because there is less soot clogging up the exhaust, sticking to the valves, dirtying the oil, wearing the rings, etc. As long as you aren't pushing the engine harder due to it's increased output, I would think it would last longer.

If NA diesels lasted longer and/or were more efficient, you'd see all of the commercial trucks, railroads, and large commercial ships running without turbos.

Earlier, someone mentioned not liking turbo gas engines, presumably due to some bad experiences with them. I know of a number of performance shops that build extremely reliable high hp street and race engines that are as docile as any commuter car, idling at 700 or 800 rpm, yet making upwards of 1,000 or 2,000 hp at 7,000 rpm. These engines are built from the ground up for turbo use, with all forged internals and dual stage injection systems. Yes, they have shorter lives than an identically sized NA engine if driven to their limits, but if you determined that the NA engine produced 675hp, and used the ECU to limit the turbo'd engine power to that same level, you might very well find that the NA engine died first, due to being run at max. power, yet the more powerful engine is still purring along, running at only half power.

Turbos do not kill gas or diesel engines, it's running them at WOT or under high load that shortens their lives. An engine designed for turbo use will last just as long as an NA engine under the same load, possibly longer if it's more powerful than needed.

[leftbrainstuff]

If you properly maintain a powerplant there is no real difference in turbo or naturally aspirated for durability.

I prefer a naturally aspirated diesel in my liberty 458 for its durability and simplicity. Its a torroise not a hare.

I would only consider a turbo if i was repowering and wasn't replacing the engine.

Sent from my GT-I9300 using Cruisers Sailing Forum mobile app

[leftbrainstuff]

Originally Posted by jtsailjt

I just had a 4JH2-DTE 88hp turbo-diesel completely rebuilt and the turbo cost was about 10% of the total so I don't think the additional cost is very significant compared to the benefits of smaller size and weight for the same horsepower available, along with greater efficiency. I had it rebuilt after buying the boat used, not because the engine or turbo was failing, but the previous owner had it WAY overpropped for the last 15 years and at some point had a seawater leak in the engine compartment that sprayed water around causing numerous rust spots. But the engine was still operating just fine. I plan to keep the boat for awhile and wanted to start fresh so made the decision to pay Mack Boring to essentially make the engine like new. I can't speak to the long term reliability of them but if the turbo does eventually fail, the engine will still get you home, and the cost of a turbo rebuild isn't that high. Buy the boat you like best and at least for me, the question or turbo or non-turbo isn't even on the radar as a consideration.

You'll likely find a failed turbo will not have sufficient power when you need it in a sailboat application. IMHO I wouldn't consider that a benefit.

Sent from my GT-I9300 using Cruisers Sailing Forum mobile app

[a64pilot]

I agree, 30 to 40 HP range, don't see the need for a turbo, but get into higher HP ranges and turbos make much more sense.
I would guess around 100 hp + or - and I'd rather have a turbo, 60 or 80 HP or so it could be a toss up.

[socaldmax]

Originally Posted by Cheechako

Some people have had good luck with Turbos, but there have been many a thread on here about Yanmar Turbo issues. Turbos work the engine harder, and often shorter life can result. I figure it this way, if you get a 50 hp non tubro engine the HP comes from true displacement, if you get a 50 HP turbo engine, the displacement is less (you're getting a smaller engine), and it is maxed out to produce the HP.

Another way of looking at it is if you get the same displacement engine either in turbo or non turbo flavors, the turbo engine will be probably 50% more powerful and will push the same load with less strain on the engine, as well as running smoother and quieter. With my Duramax engine, there is a certain boost level (about 7 or 8 psi and up) that almost completely eliminates any engine noise and all you hear is the whoosh of the turbo compressing air, just like the big rigs. After owning a NA diesel engine powered vehicle, a TD and a gas V12 engine, smoothness (to me) seems almost synonymous with power (aside from top fuel dragsters.)

[a64pilot]

Actually if a turbo engine of identical displacement etc is run at the same power level as a non turbo, it will significantly outlast the NA. .Reason is the cylinder head and exhaust temps are lower, due in part to air being blown through the combustion chamber when both valves are open (overlap).
Turbos can definitely shorten the life of an engine if they are used to increase the HP of the engine too high and the engine is operated at that high power level. That's the reason I wouldn't have a turbo airplane engine, engine life span is too short

[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.

[valhalla360]

Originally Posted by socaldmax

Another way of looking at it is if you get the same displacement engine either in turbo or non turbo flavors, the turbo engine will be probably 50% more powerful and will push the same load with less strain on the engine, as well as running smoother and quieter. With my Duramax engine, there is a certain boost level (about 7 or 8 psi and up) that almost completely eliminates any engine noise and all you hear is the whoosh of the turbo compressing air, just like the big rigs. After owning a NA diesel engine powered vehicle, a TD and a gas V12 engine, smoothness (to me) seems almost synonymous with power (aside from top fuel dragsters.)

I haven't priced them but I would assume a 40hp NA engine is significantly cheaper to purchase than a 60hp turbo with the same engine block. Assuming you aren't correcting a power deficency, it's not a logical change.

In terms of a cruising sailboat, the more logical comparison would be a NA 40hp vs a turbo 40hp with a smaller block in the hopes of reducing weight without impacting reliability.

[hpeer]

Originally Posted by Artful Dodger

Personally being a diesel mechanic I would prefer no turbo as once you have turbo problems your toast out there. With a pump or injector issue I can limp in. Here in Canada the fellow before we bought our boat had to install a new turbo, that once done was around, $2,500, something I think was a bit over priced. Myself I always consider if it breaks what can I do to get by, if turbo is gone nothing.

This was banted around here a year to two ago. IIRC there was some guy down in the Carib who had a blown turbo, and he couldn't or didn't get it fixed for something like 8 months. He said is just not a problem, he ran the engine, got lower horsepower, but it ran fine with a dead turbo.

Or are there other failure modes????