To TURBO or not to TURBO

Thought I would drop in and ask a question if you don't mind.

I am moving over from a sailboat to a power boat. My first thought was a trawler displacement hull, but then I started looking at semi-displacement hulls and heard a bunch of stories that those boats with turbo diesels could go at trawler speeds and not hurt the engines. Or, you could go slow for a while then you had to go fast. And, if you bought one from someone, you had to make sure they did it right when they had it or the engine would be used up.

I know there are semi- displacement hull boats that have naturally aspirating type diesels and that they can handle slow speeds better.

So, my thinking is that a non turbo diesel is better than a turbo diesel for slow speeds on a boat that can reach planing speed. Is this correct?

Really to general a question. It depends a great deal on the motor and at what RPM it's turning at slow cruise. You will reach a slow enough RPM with just about any motor where it won't be happy regardless of turbo or not.

Ted

Suppose I wanted to take a 46' Searay (27500 lbs) with a pair of 6V92 DD Turbo and run it at say, 10 knts (mind you this is for fuel economy purposes)

or

a 40' semi displacement hull like a Viking with a pair of turbo 225 Lemans running it a 10 knts all day.

Are those acceptable compared to a Bertram with pair of DD 871's naturally aspirated running at the same 10 knts?

One reason I bought my boat is because it has naturally aspirated 175 hp Hinos. I didn't want the extra problems that can happen with a turbo, even though I give up some hp and they're less efficient. I believe with proper maintenance and operation a NA engine will give a longer trouble free life than a turboed unit. The reason I believe this is I've replaced many failed turbos over the years and a few did damage to the engine when they failed, I was looking for what I thought would be the most dependable.


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None of the the DD 2 stroke series are naturally aspirated they all have blowers to charge the cylinders and scavenge the exhaust gasses.


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Turbos also whine - depending on the acuity of your hearing that can be noticeable.


Keith

CWC-we have a full displacement boat with twin 158 HP John Deeres w/turbos. We cruise at about 1600 RPM and seldom get above 1800. WE have never had any problems. Never have noticed any whine, but then our ER is pretty well soundproofed.

I`ve had both. Keep it simple, NA, not turbo. But if you find a great boat at a good price, with turbos, don`t let it stop you, just balance everything up.

Not a deal breaker for me, but I prefer naturally-aspirated to keep it simpler. My NA 80-hp John Deere meets the boat's power needs.

THD said:

CWC-we have a full displacement boat with twin 158 HP John Deeres w/turbos. We cruise at about 1600 RPM and seldom get above 1800. WE have never had any problems. Never have noticed any whine, but then our ER is pretty well soundproofed.

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Q? would the engine be under boost @ 1600/1800 rpm ? maybe not

Hi
With our current vessel which has twin Cat 3406 540 hp turbo which rev out at 2000 rpm, we cruise at 1200 rpm at 9.6 knots, so they are not ideal for load and are working very lightly.We just completed a 2500 mile cruise , and all we do is every 4 or so Hours put the hammers down for 5 mins to give them a run. We have not experienced any issues with the engines. What we do like about the engines are that when we require some additional power , in say crossing a bar etc, it's there. They are also very quiet just purring along. Depending on your gearboxes, ours are twin disc, we often run on one engine, which helps apply a bit of load, and the other windmills, you can do this for quite a few hours, just need to be mindful of oil temp in the windmilling box
You can also purchase an additive, de carboniser that may assist in keeping the cylinders clean and prevent glazing.
Our last vessel had the same overpowered approach with a full displacement hull 50 foot with a pair of cummins turbo 6bta 210 hp each , again we cruised at 1650 rpm at 9.3 knots and these revved out to 2200 rpm, and again we had 5 years of trouble free boating using the same approach, give them a run at wot every so often and at least once every time we went out.
Booth vessels we brought as used vessels.

Cheers Chris D
I see no issues with a turbo engine.

IIRC the 3406 was designed for the trucks building the Alaska Highway,
they were spending long periods at idle.
Nice engines for driving.

Ted

"None of the the DD 2 stroke series are naturally aspirated they all have blowers to charge the cylinders and scavenge the exhaust gasses".

True , but the blower leaves almost zero above atmosphere pressure in the cylinder by design..

The question is really do you need the extra power a turbo can create?

If you have a boat that can get up on top and go, 20-40K a turbo will be required to keep the engine light enough .

To make wakes and wallow along at SD speeds 12-15K a turbo is not required to give the under 1nm/g fuel bill.

A turbo would be fine with a small enough engine that it was required for normal cruise , but these are rare.

The turbo must have positive boost to run clean, and in many cases that is faster than you wish to pay for in diesel.

If its a must for boat speed they are worth the extra expense , otherwise , what is not there cant break.

River Cruiser said:

None of the the DD 2 stroke series are naturally aspirated they all have blowers to charge the cylinders and scavenge the exhaust gasses.


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A blower is not a turbo. Indeed there were "N" model Detroits without turbos.

As for the OP, there is probably more internet lore and dockside legend on this subject in general than even, dare I say, anchors.

I was happy to find out from a diesel mechanic that our Volvo TMD 31A could have the turbo removed if it ever became a problem. Also he commented that that model Volvo is a great engine, always good to hear.

With but rare exception, the only way to get a legal non turboed diesel engine is on the old boat used market. Keep those old Lehmans and 4 cylinder JDs running if you wish to keep the distinction of being turbo free. The comparison to the anchor debate best be phrased " do I really need an anchor?"

Heck even the almost perfect VW 2 liter TDIs in cars use them, to great success if one is to read a different thread on TF. Millions of gas and diesel turbo charged engines are produced every year with nothing but benefits.

Why the debate over a successfully used engine intake design approaching one century in use? A bit of historical research on the subject may be helpful CWC.

Thanks everyone, and I am trying to do as much research as I can. Most of what I find is that, by manufacture design, most engines match the hull design. Displacement hulls, older ones that is, come with lower HP NA diesels. But when you get to planing hulls the engines increase in HP, needing turbos, to match the hull design for speed. Trying to determine if a fast boat can economically (fuel wise and part wise) operate at slow speeds is rather hard. There are engine specs for newer boats and engines but, I have to look at older boats to be in the game.

I don't need to operate at ski boat speed. Having a boat that can get on top some of the time would be nice, but that would be on occasion. Most of the time trawlering along would do me just fine. Finding that boat and engine combo is pretty hard.

Trying to determine if a fast boat can economically (fuel wise and part wise) operate at slow speeds is rather hard.

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No, it's not hard. But first you need to define what "economically" means. Some depends on the engines, a lot depends on the boat.

My big fat Hatteras was designed to run on "plane", (theoretically about 14 knots) but we virtually never did. 8-9 knots wuz us. We ran it up at the end of the typical day for about 10 or 15 minutes. Engines surveyed out beautifully after 2000+ hours of running that way. I know a lot of other Hatteras MY owners, and all but one run it the way I described.

Sunchaser described the whole turbo issue quite well. You could subscribe to boat diesel.com for more detailed info.

Sun chaser, do some research on the Cummins 6.7 used in the Dodge Ram, EPA and others total screwed up a great Diesel engine. DPF clogging up, turbos destroyed by recirculating exhaust gases to meet requirements. Now new big trucks required to have DPF causing break downs on the big rigs and repair bills in the thousands. I also have heard new boat Diesel engines have to be equipped with DPF. (Diesel Particulate Filters) Sure glad I have this old Volvo TMD 31 A !!!

cwc said:

Thanks everyone, and I am trying to do as much research as I can. Most of what I find is that, by manufacture design, most engines match the hull design. Displacement hulls, older ones that is, come with lower HP NA diesels. But when you get to planing hulls the engines increase in HP, needing turbos, to match the hull design for speed. Trying to determine if a fast boat can economically (fuel wise and part wise) operate at slow speeds is rather hard. There are engine specs for newer boats and engines but, I have to look at older boats to be in the game.

I don't need to operate at ski boat speed. Having a boat that can get on top some of the time would be nice, but that would be on occasion. Most of the time trawlering along would do me just fine. Finding that boat and engine combo is pretty hard.

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There are quite a number of older 35-45' semi-planning boats with non-intercooled, but turbocharged engines that were realistically sized for the 13-15 knot speed range. Ocean Alexander built a lot of them....Grand Banks in the mid-years...the tugs are another example. When the push for more speed began in the late 80's and early 90's, many manufacturers added intercoolers to the same engines to squeeze out a few more knots. Given that you're thinking in terms of a slow plane capability, these overpowered semi-planning or full planning hulls might not float your boat....more complex and truly operating way off design spec when run in the hull speed plus range. I'd recommend that you look at the prop curve for boats under consideration and compare power required for your desired operating speed range to the installed power. If it takes 300 HP to cruise at 14-15 knots and installed power is 750 HP, the boat has too much engine for your needs...especially since it's going to spend most of it's life blubbering along at 65 total HP at hull speed. Of course the same argument could be made for NA engines....but realistically, they don't exist as the physical size and weight are prohibitive. Modern engines with sophisticated fuel controls (NA or turbo) are another animal.

semi-planing said:

There are quite a number of older 35-45' semi-planning boats with non-intercooled, but turbocharged engines that were realistically sized for the 13-15 knot speed range. Ocean Alexander built a lot of them....Grand Banks in the mid-years...the tugs are another example. When the push for more speed began in the late 80's and early 90's, many manufacturers added intercoolers to the same engines to squeeze out a few more knots. Given that you're thinking in terms of a slow plane capability, these overpowered semi-planning or full planning hulls might not float your boat....more complex and truly operating way off design spec when run in the hull speed plus range. I'd recommend that you look at the prop curve for boats under consideration and compare power required for your desired operating speed range to the installed power. If it takes 300 HP to cruise at 14-15 knots and installed power is 750 HP, the boat has too much engine for your needs...especially since it's going to spend most of it's life blubbering along at 65 total HP at hull speed. Of course the same argument could be made for NA engines....but realistically, they don't exist as the physical size and weight are prohibitive. Modern engines with sophisticated fuel controls (NA or turbo) are another animal.

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Sounds to me like you said, get a boat with less engine (lower HP) and work with in its range. Is that a fair interpretation?

Our boat has Cat 3406C's, turbo'd at 580hp. When I bought it a very reliable diesel mechanic said I should run at 80% throttle about 20% of the time and the rest of the time they could be idled.


RE: Ted's comment about the Cats, I was told by the mechanic that these engines were designed to go a million miles in an over-the-road truck before they would need any major overhaul work. He said that would equate to about 100,000 hours in a boat. I somehow don't think I'll ever reach that many hours.


I usually run around 1000-1050 rpm's and that gives me about 10-2-10.5 kts which seems to be a very efficient speed/rpm range. The nice thing about having the turbos is if I want to jump up on plane to get somewhere faster, I can bump up the rpm's to about 1750 (80%) and that kicks the speed up to around 22kts.


As to the sound of the engines when they're running on turbo, I can hear the engines but don't hear any whine from the turbos. That whining sound I hear is from the fuel pumps running at high speed!

As expected, this thread has turned out like an anchor thread- information, misinformation and lots of opinions. Let's try to sort through these:

First you can buy a Tier 3 marine engine for a new build without a turbocharger, but probably not in your size range. Yanmar has a new line of common rail injected 2 liter engines that produce up to about 50 hp that meet Tier 3. But that engine is probably only suited for a very small trawler. There may be some others, maybe John Deere, but not at 200+ hp levels.

A displacement speed hull trawler is typically fitted with about 2 hp per 1,000 lbs of displacement. But none of the boats you mentioned are displacement hulls. So if you want to go fast - maybe 15 kts or so when you want to go fast and slow down to displacement speeds of 7-8 kts when you want to go slow, this will take a turbocharged engine.

So can you run a turbocharged engine slow? Absolutely yes. The gurus at boatdiesel have been saying this for years. Why for heavens sake, can't I run my Yanmar 5.3 liter turbocharged high output diesel at 1,600 rpm to go slow on my boat but it is ok to do that on a 5.8 liter Ford Lehman. You just need to run it at enough power to keep the engine up to operating temperature.

The Detroit Diesel two cycle engines are a special case due to their design. They don't like to be run slow at low power settings. If they are they will slobber which means producing lots of unburned fuel that builds up in unwanted places. More than anything else probably DD's are responsible for the "run them hard" old wives tale.

The other objection to turbocharged engines is that they fail. Well turbos themselves don't fail unless something external causes them to fail. They rarely fail on over the road trucks. The biggest cause of failure in a marine engine is seawater intrusion caused mostly by a poorly designed exhaust system followed way back by a leaking after cooler.

Lots of boaters out there have poorly designed exhaust systems and many already have damage to their turbo. They just don't know it yet. Boat manufacturers take the easy way out, abetted by the engine manufacturers. Hang out on boatdiesel for a while and you will find lots of examples. The only way to deal with the problem is have a better system designed and built for your boat. The cost will be $1000-5000.

Unfortunately sea water cooled after coolers are fitted to probably 95% of the 100 hp and greater engines on the market today for new builds. But a proper maintenance schedule with meticulous servicing protocols will largely eliminate this problem.

If you are looking at older boats. then there are some engines available that avoid the aftercooler problem. The 210 hp Cummins 6BT has no aftercooler and the 270 hp model of the 6BTA uses glycol coolant like trucks so failures are rare.

But when you get up to 50 hp per liter or greater, turbocharging with a sea water cooled aftercooler is about the only way to go.

Sorry this has been so long, but hopefully I got a lot of useful information packed into it.

David

HiDHo said:

Sun chaser, do some research on the Cummins 6.7 used in the Dodge Ram, EPA and others total screwed up a great Diesel engine. DPF clogging up, turbos destroyed by recirculating exhaust gases to meet requirements. !!!

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I feel your pain. My first experience with DPFs were nearly 40 years ago in underground mines. Probably used at least 5 different sizes of Donaldson's units on dozens of pieces of diesel equipment whether turboed or not. Plugging of the units as I recall were common on the lightly used equipment where off gas temperatures were not high enough to allow the regeneration cycle to work right.

It is indeed a tough situation for some diesel owners, but how is it related to turbo vs non turbo charged engines?

Liberty2015 said:

Hi
With our current vessel which has twin Cat 3406 540 hp turbo which rev out at 2000 rpm, we cruise at 1200 rpm at 9.6 knots, so they are not ideal for load and are working very lightly.We just completed a 2500 mile cruise , and all we do is every 4 or so Hours put the hammers down for 5 mins to give them a run. We have not experienced any issues with the engines. What we do like about the engines are that when we require some additional power , in say crossing a bar etc, it's there. They are also very quiet just purring along. Depending on your gearboxes, ours are twin disc, we often run on one engine, which helps apply a bit of load, and the other windmills, you can do this for quite a few hours, just need to be mindful of oil temp in the windmilling box
You can also purchase an additive, de carboniser that may assist in keeping the cylinders clean and prevent glazing.
Our last vessel had the same overpowered approach with a full displacement hull 50 foot with a pair of cummins turbo 6bta 210 hp each , again we cruised at 1650 rpm at 9.3 knots and these revved out to 2200 rpm, and again we had 5 years of trouble free boating using the same approach, give them a run at wot every so often and at least once every time we went out.
Booth vessels we brought as used vessels.

Cheers Chris D
I see no issues with a turbo engine.

Click to expand...

CWC

I agree with Chris D, I have twin 3208T 330hp Caterpillars NON AFTERCOOLED, I run them between 1300-1500 RPMs depending on wind/current to get 7.0 -8.0 knots and about every 4 hours spin them up to WOT (2800 RPMs) for 3-5 minutes then back them down to 2300 (cruise RPM) for 10 minutes or so....then back down to hull speed. If I need it I have the reserve HP but otherwise we just "trawler" along....

Good luck with your search...

Dave

cwc said:

Sounds to me like you said, get a boat with less engine (lower HP) and work with in its range. Is that a fair interpretation?

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Of course. It's difficult enough keeping a fairly small horsepower turbo engine at operating temperature. I have twin 250s in a 32,000 pound semi-planning hull. At 8.5 knots, the engines run in the 165-170 degree range making about 65 HP (total!). Run them up to rpm for 14 knots and the temp climbs to 180-185 (and holds that on up to max rpm...18 knots). Put a pair of 375-425 HP boat anchors in there and the problem sure won't get any better. But that's exactly what the factories were doing starting in the late 80's. Actually, our boat would be ideal with a pair of modern NA''s in the 200 HP range or a single 400 hp turbo. Not quite worth it until fuel price gets back up to $5-6 per gallon. But the boats just begging for a swap are those really nice 45-50 foot SD hulls with old tech twin 375-425s.

Again, thanks for the tips. Based on what has been said here, I think I am going to look for the boat I like and not put so much efficiencies on the engine. Just make sure the boat and engine match my needs.

cwc said:

Again, thanks for the tips. Based on what has been said here, I think I am going to look for the boat I like and not put so much efficiencies on the engine. Just make sure the boat and engine match my needs.

Click to expand...

Good thinking!!!

David

The Detroit Diesel two cycle engines are a special case due to their design. They don't like to be run slow at low power settings. If they are they will slobber which means producing lots of unburned fuel that builds up in unwanted places. More than anything else probably DD's are responsible for the "run them hard" old wives tale.

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Well, that's pretty much of an old wive's tale in and of itself. Someone forgot to tell my engines that as well as a few thousand others. They actually like it just fine, especially if you run them up at some point during the day for a few minutes... nice but not completely necessary. Those old Detroits have done thousands of hours at trolling speed in commercial and recreational fishing applications. I've never met a Detroit mechanic, and I've known a few really good ones, who saw an engine fail due to low speed usage. But a lot from being run on the pins.

Yep, Detroits can run light load dang near forever. Nothing really different about them and light load compared to four strokes.

To the OP, there 437.5 things more important on selecting boats and engines than whether engine has a turbo or not. Turbos are very reliable, and at light load they just coast along, not making any real boost, and not doing any harm either.