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Old 10-10-2016, 10:18 AM   #1
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Repowering old steel trawler

Ok.. here is my first post...
I'm almost ready to close the deal for an old steel trawler. Past saturday I spend 3 hours checking hull structure with an ultrasound tester, open hatch, looking for rust... I found some but it's under control..
For the price, I want to replace engine. Right one, trawler have a tired detroit il6-71. I know that engine intimately and an overhaul is out the question... that thing take diesel like crazy. Engine have very low hours (around 1000) but I make my mind to replace for... (here my question).. wich one??
yanmar?? lugger?? cummins?? volvo??
Actual engine is 170 hp and give more or less 8 knots at full power. Hull speed is 9.7 so I would install something a little more power (close to 200 hp) but compact in order to reach full hull speed.
Suggestions??
Thanks you in advance!!
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Old 10-10-2016, 11:21 AM   #2
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What is boat length/ weight?

If you want to cruise at 9.7 you might be needing about 250hp there. Not a 250hp engine, but 250 at cruise.

My vote would be for Cat 3406 or Cummins 855/N14. Either can be found in a variety of ratings, but regardless of max hp, either would be very happy making 250hp.
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Old 10-10-2016, 11:49 AM   #3
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My vote would be for Cat 3406 or Cummins 855/N14. Either can be found in a variety of ratings, but regardless of max hp, either would be very happy making 250hp.

Ski

A few years ago I was considering taking a vessel to survey that had the 855NT14. I backed off due to exhaust manifold leaks. According to some Cummins experts that issue is not easily resolvable. Your thoughts?
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Old 10-10-2016, 11:55 AM   #4
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Welcome, garrobito, and congrats on your steel boat.

Can't blame you for wanting to replace that 6-71, even if it's still running. The 3406 that Ski suggests is a strong contender, but look at your engine compartment dimensions carefully. Even though it's a straight six, it's a physically big engine. Parts and service can be pricey (it's a Cat, after all), but RTOs are sometimes advertised in Boats & Harbors by commercial operators looking to hitch-up a few more Mr. Eds.

Volvo marine diesels deserve their poor reputation - avoid 'em.

Yanmar has offerings in your horsepower range. Every one I've ever experienced has been satisfactory, and I have never heard a single word of complaint from anyone else who runs them. Same with Luggers, Cummins a bit less so, but at 220 hp, the ubiquitous 6BT 5.9 slots right into the specs you're talking about. Remanned engines seem widely available.

Good luck, keep us posted on your purchase, and maybe post some pics when you get a chance.
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Old 10-10-2016, 01:44 PM   #5
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Ski

A few years ago I was considering taking a vessel to survey that had the 855NT14. I backed off due to exhaust manifold leaks. According to some Cummins experts that issue is not easily resolvable. Your thoughts?
I must admit I don't know the marine 14 in super detail. A couple commercial boats running them and have not heard any issues. There could be a problem out there. One I know is running a dry exh manifold and turbo with keel cooling, owner would let me know if it was acting up.

I think the B210 is too small here. It would have to run wide open to put 200hp down the line.
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Old 10-10-2016, 02:05 PM   #6
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garrobito, I ran your numbers quickly, and your vessel at 52' LWL and 66 long tons, would require about 330 bhp to make full steam ahead 9.7 knots.

The previous owner setup that boat for his operating speed of probably about 7.25 to 7.5 knots. At that speed the engine was running about 75% to 80% output and was a happy engine. He had a little bit of reserve power for sea conditions, and if the seas got too rough then he probably throttled back anyway, like most.

A good question to answer honestly is what is your desired operating speed? 9.7 knots is going to cost you a hell of a lot in engine/gear/prop (and possibly shaft/stuffing box) upgrades - as well as fuel.

BTW, for the other contributors here, what's the matter with a 6-71???
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Old 10-10-2016, 02:19 PM   #7
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Makobuilders wrote: "BTW, for the other contributors here, what's the matter with a 6-71?"

In my experience, newer four-cycle diesels are cleaner, quieter and (increasingly) more fuel efficient. That said, every two-cycle Detroit I've ever run was as reliable as an eastern sunrise. Once started, they run as long as you keep them supplied with air and fuel. And, parts interchangeability among the Detroit line makes them readily fixable. If the mere presence of a Detroit was the worst thing about a boat I otherwise wanted, I would likely take it and run it indefinitely. But, as the OP is faced with what he describes as a "tired" example of the breed, the choice to remove and replace it wouldn't be hard for me.
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Old 10-10-2016, 02:53 PM   #8
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I hate to challenge your expertise but if it were me and I knew detroits as you do I would run it for some years and then decide what to do.

There are many things on which to spend money on a new to you boat but a running engine would not be high on my list.
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Old 10-10-2016, 03:04 PM   #9
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One I know is running a dry exh manifold and turbo with keel cooling, owner would let me know if it was acting up.
.
The setup I'm familiar with is the same. But in a yacht pristine engine room the dry exhaust manifold had a few soot leaks that over time failed the "white glove" trick.
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Old 10-10-2016, 03:11 PM   #10
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as a direct answer to your question a low revving engine producing the needed power would be my choice. Preferably one with the fewest different metals in the cooling system.
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Old 10-10-2016, 03:11 PM   #11
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The OP did not ask if he should keep the DD, he asked for alternatives. The engines Ski mentioned are good choices as is the ubiquitous JD 6081 used extensively in the Nordhavn line.
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Old 10-10-2016, 03:40 PM   #12
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Great discussions thanks!! Nothing better than a bunch of fellas who already passed this type of decisions..
Today I was at Yanmas dealer... they offer me the 6BY3-260 with yanmar transmission, all electronic include, crated (installation is another number) for (final) 26K.
I think it's a good number, specially because the commercial type (have 300 hp) have a price close to 40K.
Makobuilder, I hear you and I think you're right... I think 260 hp it's the absolute minimum for this boat (46' x 15', around 20 tons displacement).
I have certain reserve about yanmar and if is possible to run days and days at 75/85% power under any circunstance.
My heart is with Lugger but they not provide any engine for that hp range..
Engine room is huge!! and I meant it... specially because I gonna remove an old generator off service from there so I can put any engine without think too much about space.. redo the bed engine it's gonna require some welding (nothing mayor I expect) and I can use that time to paint again the whole area and install better insulation.
Volvo is out the question for price.. carterpillar, cummins and I gonna take a decision,.. January it's gonna be the month to do the switch.
About the 6-71... well.. have few hours but I feel it's old technology (basically it's a gigantic 2 cycle engine) and even I can do the on-site overhaul almost for myself, I prefer do the repowering now and use this boat for the next 10 years without a worry.
Like I say before, the low price on the sell allow me to invest on a new engine...
This boat specifically is gonna be seated at Seattle and used mostly to explore Alaska the next 2/3 years before move down to Panama or Costa Rica...
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Old 10-10-2016, 03:53 PM   #13
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[QUOTE=garrobito;487648] Today I was at Yanmas dealer... they offer me the 6BY3-260 with yanmar transmission, all electronic include, crated (installation is another number) for (final) 26K. [QUOTE]

This is a 4000 RPM water ski engine.
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Old 10-10-2016, 04:04 PM   #14
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[QUOTE=sunchaser;487652][QUOTE=garrobito;487648] Today I was at Yanmas dealer... they offer me the 6BY3-260 with yanmar transmission, all electronic include, crated (installation is another number) for (final) 26K.
Quote:

This is a 4000 RPM water ski engine.

..yes, it's one of new high speed diesel.. I have some reserve about how long could run without pop up a cylinder...
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Old 10-10-2016, 04:09 PM   #15
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I have to laugh at the Yanmar dealer suggesting the 6BY for your boat. That is a three liter engine and it will be screaming its pants off to produce 200 hp.


You want a big, heavy, slow reving diesel for your boat. The Cat 3406 is a good choice. At 15 liters or so it s big and heavy and it will easily put out 200-250 hp while purring along at 1/3 the rpm of the Yanmar. But at 250 hp you will burn more than 12 gph.


But as others have noted, I doubt that you will cruise using 200 hp or more. Slow down a knot or so, and your power and fuel consumption will drop in half.


If you can live with 200 hp or less continuously, also consider a remanned Cummins 6CTA. Essentially a factory new engine with full Cummins warranty.


David
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Old 10-10-2016, 04:35 PM   #16
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Your Yanmar salesman is desperate for a sale, but his motors are far from what your vessel requires.
David's comments above are right on!
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Old 10-10-2016, 04:35 PM   #17
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I have to laugh at the Yanmar dealer suggesting the 6BY for your boat. That is a three liter engine and it will be screaming its pants off to produce 200 hp.


You want a big, heavy, slow reving diesel for your boat. The Cat 3406 is a good choice. At 15 liters or so it s big and heavy and it will easily put out 200-250 hp while purring along at 1/3 the rpm of the Yanmar. But at 250 hp you will burn more than 12 gph.


But as others have noted, I doubt that you will cruise using 200 hp or more. Slow down a knot or so, and your power and fuel consumption will drop in half.


If you can live with 200 hp or less continuously, also consider a remanned Cummins 6CTA. Essentially a factory new engine with full Cummins warranty.


David
yes, I have my reserves with high speed diesel... The cummins 6cta at 350 hp could be a good one.. I know the cat 3406.. big monster... I prefer something more compact... Reliability is for me THE most important factor at this point... but I do not want to spend 10 gallons/hs later... (that's why MTU is not on my list..
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Old 10-10-2016, 04:36 PM   #18
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I had a 6BT 5.9 Cummins tuned to 250 hp, a mechanical engine. I liked it. They should be pretty cheap after a reman.

Coastie snipe (Engineman...Engineperson?) swore by the 3406. My take is straight 6, which both are, so only one head, one manifold and so forth, easier to maintain is the way to go. If you can get the hp/torque you need w/o a turbo, that, to me is a big plus. To get your hp out of a 5.9 Cummins it will have to be pumped up with a turbo, but perhaps no turbo with the 3406.

I agree with the comments about Volvo, Yanmar. With your monster engine room as described....the 3406 sounds good.
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Old 10-10-2016, 04:44 PM   #19
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Your Yanmar salesman is desperate for a sale, but his motors are far from what your vessel requires.
David's comments above are right on!
Cat 3406

..I think it's simply ignorance.. same way when you go at Home Depot.. or you know exactly what you need or rely on as associate who mostly time ignore the trade...
That's why forum are the best tools for the trade.. you can compare first hand with different owner different experiences about this..
Repower a boat is a significant investment on time, money, etc, etc... I want to do this on January but first off course I gonna do my part and read and investigate as much as I can...
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Old 10-10-2016, 07:00 PM   #20
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Run the boat for a while with the 671 and figure out how much power you want going down the shaft. Measure your fuel burn rate in gal/hr at your desired cruise and multiply it by 17, that will give you roughly what hp is being created.

You don't want to pick an engine too large or too small.

Most engines do the best at 30-70% of their rated hp.

So if you are going to run at 50-120hp, the B210 Cummins would be happy. If you don't mind a computer engine, QSB 230hp same basic size.

100-250hp, C series Cummins is good.

150-300hp, Cat 3406

The above engines in those ranges make 18-20hp per gal/hr.

Got to know what boat likes as a cruising speed first.
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