To TURBO or not to TURBO
- Thread starter cwc
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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.
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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Liberty2015
Senior Member
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- Liberty
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- 57 foot Halvorsen
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.
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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John
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.
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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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.
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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Chris
My post to 'John' above was in answer to your question. Apologies for brain fart
Mainship400
Veteran Member
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.
Mainship400
Veteran Member
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
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.
David
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.
David
