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Old 10-08-2015, 01:57 PM   #21
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Originally Posted by semi-planing View Post
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.
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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Old 10-08-2015, 02:05 PM   #22
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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! :-)
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Old 10-08-2015, 03:39 PM   #23
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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
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Old 10-08-2015, 03:44 PM   #24
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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. !!!
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?
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Old 10-08-2015, 04:45 PM   #25
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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.
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
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Old 10-08-2015, 04:59 PM   #26
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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?
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.
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Old 10-08-2015, 05:43 PM   #27
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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.
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Old 10-08-2015, 06:28 PM   #28
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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.
Good thinking!!!

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Old 10-08-2015, 06:52 PM   #29
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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.
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.
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Old 10-08-2015, 07:07 PM   #30
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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.
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Old 10-08-2015, 08:49 PM   #31
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Yep, Detroits can run light load dang near forever. Nothing really different about them and light load compared to four strokes.
I stand corrected.

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Old 10-09-2015, 04:28 AM   #32
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I am running twin Tier 2 John Deere 6068's, turbo but no aftercooler, with 201 HP each. The dealer and the factory manual both made it clear that the extended run-in period, using their break-in oil, was critical to the life of the engines. Essentially, and from memory, it was to run the engines at 60-80% load for the first 100 hours. Obviously some time at higher loads and some at less was OK, but it was key to avoid idling as much as possible. After the first 100 hours and normal oil was installed then there are no real limits on running them slow or lightly loaded. No need for end of day high power burst, but no harm doing it either.

I find myself typically running in the 30-40% engine load range, because that's all the boat needs to cruise at good speeds. Perhaps more lightly loaded than ideal but purring very economically. The engines are downsized from the ones I replaced and I can no longer get to 16 kn, which is fine by me. I didn't like the gph burn at 16 kn, and it really needed more power (and even higher gph burn) than was originally installed to get beyond the 'semi-planing' (= 'ploughing'/humongous wake) 16 kn scenario. It would probably take at least 800 HP for that, which I would hardly ever have used.

Now its a different situation if you buy the boat with all that HP installed. My take is that if a modern engine was run-in correctly then using it lightly loaded will be fine. Info from experienced posters above support this. The difficulty with a used boat, in relation to their engines in particular, is knowing how they were treated in the first 100 hours. Dealers may be able to plug into the ECU and tell you quite a lot though. That first 100 hours did seem to be a long time, and I'm glad I got it done in the first decent cruise to Desolation Sound etc.

Although my boat ex: factory was claimed to be 48,000 lb, its a bit over 60,000 lb now (mid-load condition). The size and weight bring comforts, I sacrificed speed because I'm a cheapskate regarding visits to the fuel dock.

Advice to the OP to first find the boat that fits, and look and engines and other things second makes sense to me. If there is an occasional 'need for speed' feeling then stay under about 40' and look for a relatively light weight, and then the fuel-dock pain won't be too severe.
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Old 10-09-2015, 04:36 AM   #33
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Brian,

Just as a matter of interest , what fuel consumption to you get at say 9 knots, Liberty averaged 38 litres per hour combined on our Tassie trip of 2,500 miles. I was pleased with this considering the size of the engines.

Cheers Chris D Liberty.
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Old 10-09-2015, 06:37 AM   #34
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Closest data point I have from sea trials after refit is:
8.9 kn, 1750 rpm, 22 litres per hour (combined engine consumption)
That was clean hull etc, a bit over mid-load fuel. The JD's are far superior to the old Cummins I had at those kind of speeds. I regard 9 kn as my 'sweet spot'.

These days I always have current for or against in the Brisbane River and Moreton Bay. But I need to find some slack water and re-do some of the tests. My feeling is that PropSpeed has made a noticeable difference, beneficial, to fuel use at the mid to upper rpm. Also, coming home last Monday, whilst still in the Bay I went up to 2500 for a bit and saw 12.4 kn steady on the GPS. Some of that was current-assist, over 1 kn for sure but still it was faster than I expected.
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Old 10-09-2015, 09:55 AM   #35
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with reasonable sized engines I don't think you will find many boats that will really plane without turbos. If you compare the same engine in the same boat with and with out turbos the fuel use at bow down speed will be virtually identical. My last boat weighed 38,000 pounds at 44' and had twin 430 HP turbo engines. It did 2+ NMPG at 8 knots or so and would hit 23 at wot.


To me that was perfect for crossing open water quickly and avoiding storms while I was happy at slower speeds in ICW or unhurried offshore passages.
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Old 10-09-2015, 06:28 PM   #36
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Brian,

Just as a matter of interest , what fuel consumption to you get at say 9 knots, Liberty averaged 38 litres per hour combined on our Tassie trip of 2,500 miles. I was pleased with this considering the size of the engines.

Cheers Chris D Liberty.
Chris
My post to 'John' above was in answer to your question. Apologies for brain fart
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Old 10-10-2015, 11:48 AM   #37
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I have had both. Agree with the other posts that say they rarely use the extra power due to fuel consumption. Turbo or not would not affect what boat I bought. But if everything else was equal, I would favor NA.
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Old 10-10-2015, 12:09 PM   #38
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I have had both. Agree with the other posts that say they rarely use the extra power due to fuel consumption. Turbo or not would not affect what boat I bought. But if everything else was equal, I would favor NA.

Have any Mainships been built in the past 15 years or so without turbochargers. How about the past 20 years? Ever?
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Old 10-10-2015, 12:21 PM   #39
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SunChaser, not sure if older Mainships were built without turbo engines. Someone on the Mainship forum could probably answer that. I am guessing the 80s vintage ones did not have turbo charged engines. When I said I have owned both types of engines, it was in reference to other boats
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Old 10-10-2015, 12:43 PM   #40
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The first Mainship that most considered a trawler was the classic 34. It was delivered with a Perkins 6.354T 165 hp engine that was turbocharged but not aftercooled. It is a rock solid engine in that configuration.

Other models were delivered with gassers and diesels. AFAIK there were no NA diesels. Mainships were always semi displacement hulls and could use the extra hp of the turbo to go faster than hull speed if desired.

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