Turbo or not?

[roland stockham]

I have to replace my engine after flooding and discoved that the smaller 3 cyl with turbo has the same power output and fuel consumption figures. Currently have the 4 cyl but the 3 would be both smaller and lighter so would be an easier fit. The 4 goes in but is definitely a 'shoehorn' job. Only ever had turbo diesels on cars so very different load profile. This engine size give generous power and will push the boat in heavy weather. Under normal conditions I get cruising speed (5kn) at 1800rpm. Max RPM on both engines is 300rpm. Price seams to be about the same

Anyone with experience of turbos on boat care to comment. Any advantages/disadvantages or maintenance issues.

[clownfishsydney]

Size of engine? Current brand, model and hp?

[Dockhead]

I have had turbodiesels on boats for years and thousands of hours. I wouldn't want a naturally aspirated diesel, which is much heavier for the same power and has a narrower range of healthy power output -- that is, is subject to bore polishing at a higher power output than a turbodiesel.

Turbochargers have exactly one moving part, and in a well designed engine they are pretty bulletproof. I've never had any trouble with mine, and I've only even known one person who had trouble with a turbocharger on a boat, and it was relatively cheap to fix, not much more than a new starter would have cost.

As a bonus, turbochargers make the engine run significantly smoother and more quiet.

The advantages of turbodiesels are so great that you can't even buy a naturally aspirated diesel in a car or a truck.

The weight of the engine has a significant effect on sailing performance, in most boats. Lesser bulk makes the engine easier to get to and service. A turbocharger allows you to use a significantly lighter and less bulky engine for a given power output.

In my opinion, turbo all the way. Others of course will have different opinions; you'll have to make up your own mind.

[Van Der Beek]

In your want to save on both space and weight Turbo is the way to go.

[roland stockham]

Thanks for that. clownfishsydney - current engine is a beta 1505, tubo would mean I coulf go to the 1105T both about 34hp @ 3000rpm intermittent rating and displacement is 7.25 long ton dry wt on 28ft LWL with mod to low windage

[MartinR]

If I could choose between turbo and naturally aspirated, I would choose the turbo anytime. Of course, it adds a little bit of complexity to the engine, but the engine runs quieter, cooler, lives longer, uses less fuel and is lighter.

Only, turbo charged engines do definitely not like to run at idle for hours.
I have never had any turbo or intercooler failure on one of my engines. (have had a few)

[Cheechako]

Turbos wear out faster and are often the max HP engine produced in a specific block size. It's trying to get the most out of the least. Traditional opinions are: "The most reliable long lived engines are the lowest HP available in a specific block size."
None of this means you cant successfully use a turbo engine though. But me?, I would always buy the lower rated engine in a block size given the choice.
I've had 3 turbo cars in my life. All 3 engines experienced wear issues prematurely. Including a Toyota Supra I loved..

From a couple of car mechanic blogs:
“Anyway, the point here is that automakers -- in a desperate bid to eek out even 1 extra mile per gallon from their vehicles -- all seem to be resorting to turbocharged engines, because they seem to offer a lot of power when you need it and a lot of gas mileage when you're just cruising. And this leads to the question: Will these engines hold up in the long run? I don't know, and it scares me to my very core.
The automakers, of course, say they will. However, this goes against just about everything that any of us who owned turbocharged cars from the 1980s and 1990s know to be true. I can't tell you how many calls I've received from mechanics over the years telling me that the turbocharger is leaking, that oil is seeping from the turbocharger, that water is flowing through the turbocharger because it is openly crying or that the turbocharger committed an armed robbery and needs a good criminal defense attorney.”

“But there’s one obvious problem with all this turbocharging: How long will these engines really last?
I say this as the former owner of a 1990s turbocharged Volvo, and then the owner of a non-turbocharged 1990s Audi. When it comes to turbocharging, here’s what I learned: Turbos add complication. They often bring more stress to the engine. They leak. They fail. They suffer from serious longevity problems. And this was a turbocharged Volvo, a forced-induction car from an automaker who had known about this technology for years. How do you think it’ll last in a brand-new pickup?
When it came time to replace my Volvo back in 2006, I didn’t want to find out. Knowing that the Audi A4 1.8T had a problem where the turbochargers would leak oil, I went with a 2.8-liter model. I’ve made it a point to generally staying away from turbocharged cars after that.”

[Dockhead]

Originally Posted by MartinR

If I could choose between turbo and naturally aspirated, I would choose the turbo anytime. Of course, it adds a little bit of complexity to the engine, but the engine runs quieter, cooler, lives longer, uses less fuel and is lighter.

Only, turbo charged engines do definitely not like to run at idle for hours.
I have never had any turbo or intercooler failure on one of my engines. (have had a few)

Some people on here will disagree about turbo engines living longer.

And they are probably right -- IF we're talking about turbo engines used at maximum power or near maximum power most of the time, like what is typical with power boats.

But for average yacht usage, which is very different from typical usage on power boats, I actually agree that turbo engines will probably last longer -- all other things being equal. That's because in typical yacht usage, you are running at no more than 20% or 30% of maximum power. You need 90% or 100% of the maximum rated power only on rare occasion when you are bashing into head seas etc.

A turbo engine will run better at 20% to 30% of max than a naturally aspirated engine of the same power, because the turbo engine will have about half the displacement and will be better loaded.

[Dockhead]

Originally Posted by Cheechako

Turbos wear out faster and are often the max HP engine produced in a specific block size. It's trying to get the most out of the least. Traditional opinions are: "The most reliable long lived engines are the lowest HP available in a specific block size."
None of this means you cant successfully use a turbo engine though. But me?, I would always buy the lower rated engine in a block size given the choice.
I've had 3 turbo cars in my life. All 3 engines experienced wear issues prematurely. Including a Toyota Supra I loved..

OK, first of all, don't compare turbo gasoline engines like Supras. That's something very different from a turbodiesel.

But second -- are you sure that the "most reliable long lived engines are the lowest HP available in a specific block size"?

What percentage of sailboat engines get worn out from using them at max power all the time, versus those which get worn out or bores polished from not running them with enough load? Very few, I would say!

To put some concrete numbers on it -- my boat could be bought with either a 100 hp Yanmar turbo diesel, 2000cc, or an 83 hp Perkins, 4000cc.

I'm typically running my boat at 1800 RPM (out of 4000 RPM redline) in calm weather, which is when most motoring gets done, using no more than 20 horsepower or so.

What is going to be more healthy -- 20 horsepower out of 2000cc engine or 20 horsepower out of 4000cc engine? Diesels don't have throttle plates, so the volume of air which passes through them is a linear function of displacement vs RPM. To use a 4000cc engine for only 20 hp means tiny little spritzes of fuel burned in those huge cylinders -- 1000cc each. The flames won't even reach all the way down the cylinders, which will stay cool.

Whereas the 2000cc 100hp turbo diesel will be running just like the 50hp naturally aspirated version would be running -- 40% of its 50hp maximum -- very healthy.

The 2000cc engine will be MUCH healthier at that level of power output. Are you sure it will have a shorter life, in typical sailboat usage, than the 4000cc engine? I'm actually pretty sure of the opposite.

If you're going to use the engine like in a power boat, most of the time at 80% or more of max power, then yes -- a bigger block will last longer. But if you only need max power on rare occasions, then a turbo diesel is ideal, and I am pretty sure will last longer, not less.

[MartinR]

And ideally you would change the stock turbo charger from original, optimised for max hp, to one with a smaller exhaust gas housing, giving better charge at lower RPM. This is a relatively cheap and efficient engine upgrade. Normally boat engines are never run at max RPM.

[a64pilot]

Turbos on boats are more like turbos on airplanes than cars, in that both can be run hard, continuously.
Here is the “catch” for a turbo motor on a boat. Vast majority of the turbo motors like big Sportfishermen a turbo can be reliably expected to cut the life of the motor in half. Reason is they are usually on boost, and high boost at that. They will typically cruise 200 off the top, meaning 200 RPM less than max or so, maybe 500. So a turbo, if it’s used, will shorten the lifespan of an engine, airplane is a prefect example, turbo motors have significantly shorter TBO’s (time between overhaul) than a non turbo, cause they are usually on boost, even if they boost only to maintain sea level power, they are on boost almost all of the time.

Now if you normally cruise your motor so that it’s not on boost, or very low boost, then a turbo motor can actually last longer than a NA motor, reason is durning the valve overlap period the slightly higher than atmospheric pressure in the manifold will blow cooling air right through the combustion chamber, lowering cylinder head temps.
Take a mythical 50 HP NA motor, run it at 15 HP for extended times as that is your cruising power, it may not be enough to fully warm the engine and cause it to “stack or slobber” google Diesel stacking or diesel slobbering.
Take an NA engine that is 35 HP, boost it to 50 with a turbo, now running it at 15 HP is enough to get it fully warmed and it won’t stack or slobber, but 50 HP is available if you need it, just use it very rarely for max longevity.

So in my opinion a turbo motor will last a good long time if you rarely use the turbo, but if the motor lives on boost, it’s going to not live nearly as long.

Turbos do add cost, complexity, more parts to break and maintain.
The component that concerns me is the salt water cooled charge cooler, if it leaks, your feeding salt water directly into the suck side of your motor.

Depends on what you like, some people like the Checker Cab type of automobile, heavy, small block Chevy, can be made to last almost forever, but does everything horribly, brakes suck, suspension sucks, comfort sucks, performance and fuel mileage sucks, but it will be still running when your dead. That is the heavy, old fashioned low RPM Diesel.

Some love a Ferrari, does everything well, but wont last forever if it used often, and in five years something else better comes along anyway. That is your newer common rail turbo Diesel.
I say common rail, cause if your going complex, go whole hog, nothing is as smooth and quiet as a common rail, the NVH (noise, vibration and harshness) of a common rail can be spark ignition engine smooth.

[nhschneider]

When I went to repower my 48' ketch, I looked high and low for a diesel that wasn't equipped with a turbocharger, as I feel a turbo isn't a good application on a cruising sailboat.

Turbos 'spool up' when exhaust gas velocities reach a certain point - that is, once an engine develops enough load, the exhaust gas velocity increases and the turbo spins, its impeller creating positive pressure in the intake manifold. However, to do this the engine usually has to be under a significant load, usually approaching three-quarters of its horsepower output. In my experience, on a cruising sailboat, that rarely happens. Sure, there may be times when you're bucking a strong current, bashing to windward, etc when you need the additional power. However, for most cruisers I know, their engine comes on when the wind dies or they're approaching an anchorage, mooring field or dock - not exactly the time when you need lots of horsepower. What this means is that the turbocharger doesn't get spooled frequently enough and can 'carbon up' to the point where if freezes.

One of the engines I was seriously considering was the Yanmar 4JH4-HTE that is equipped with a turbocharger. I read the user's manual prior to making my decision and found where Yanmar specified that the engine needed to be run at Wide Open Throttle (WOT) for at least 10% of the time it was running. I'm willing to make a big bet that this was to keep the turbo from freezing but that would have had a substantial impact on our fuel consumption. I ultimately chose the Beta Marine 90, a naturally-aspirated engine that I'm delighted with.

For many years I made my living doing heavy equipment repair, primarily agricultural and earth-moving equipment (although I did spend far too much time working on over-the-road truck-tractors). Turbochargers in those applications make a lot of sense - frequent demands for maximum horsepower - kept the turbos continuously spooled (there's something about hearing those turbos whine that I just love). But the light-duty demands of a diesel engine aboard the cruising sailboat makes the turbocharger a poorly recommend application.

Fair winds and calm seas.

[Van Der Beek]

That escalated quickly.

To Turbo or not to Turbo, that's the question.

[Fore and Aft]

It seems to me a lot of boats I survey have had the turbos replaced? Is it because they seize due to lack of use?
Cheers

[Lepke]

Exhaust Gas Temperatures are the engine killer. If you consistently run at or near yacht rated HP, the EGTs are eating away at the metals in the cylinders. If you don't run at high hp or rarely, it's not as big of a problem. But turbo engines still do not go as far between overhauls as naturals. Usually half or less.
Also dirty oil tends to build sludge in narrow passages, like the turbo oil line. If you don't change your oil...
My natural Detroit twins are 70 years old. I overhauled them. From the sleeve markings, I believe they were never overhauled previously. In talking with prior owners, the total hours were estimated somewhere above 20,000. The engines ran at rated HP or above. One owner cruised 300 rpm above rated for years. The turbo version would have been lucky to make 3,000 hours. I run at rated and expect several other owners will run them after I'm dead.