Single vs Twin: It's Baaaaack!

mahal said:

A hypothetical question to all: If you were employed as a captain by a Brokerage in Florida that needed to move one of their two new Krogen 58's to Costa Rica and the boss gave you the choice of either taking the one with twins or the single screw, which one would you pick?

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That's a no-brainer for me and my wife. We have no interest in running a single engine boat anywhere, let alone to Costa Rica.

mahal said:

A hypothetical question to all: If you were employed as a captain by a Brokerage in Florida that needed to move one of their two new Krogen 58's to Costa Rica and the boss gave you the choice of either taking the one with twins or the single screw, which one would you pick?

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Being an ACTUAL delivery captain...I would take whichever I was hired for...I've moved twins that never made it 100 yards to the fuel dock because the impellers had taken a set from 2 years on the hard...4 hrs later and I was still on my way...had it been a single..it would have been 3 hours and on my way.

Your question is idiotic...world class boats designed with one engine...ready and raring to go and you wouldn't go? I wouldn't either without tools and parts...but that would be the only reason.

I guess I'm late to this....but there was a question to me specifically, somewhere a long ways back.......

There is no better or worse, good or bad, only different answers to every users slightly different requirements. While one person's priority is maneuverability, another's is redundancy, someone else is worried about efficiency, and all are concerned with cost......

In the Gulf of Alaska a big tug with an extremely valuable tow lost power in all four engines yesterday....now the tow is on the beach.....not sure if that's 300% redundancy but it didn't help.......fuel issues were mentioned....

A number of Nordhavn's have required use of the "get home" or pony engine. The 40' that went round the world used it a couple of times, once for a cooling/wet exhaust issue......A 62' used theirs on a crossing from US West Coast to Tahiti, and found it could not quite keep the bow into wind and big sea while they dealt with a cooling/wet exhaust issue. A bit scary and Nordhavn upped the pony size after that......

A single engine/shaft/prop will cost less to install, is lower drag and deeper draft, and a single larger prop turning more slowly is more efficient than smaller diameter props turning faster......For the ultimate in propulsion efficiency see the Marco Polo line currently produced by Cheoy Lee.....one big multi-bladed prop turning very slowly with twin rudders outside it (for prop protection).....

But the single offers zero redundancy....this is not acceptable to some folks. Some are okay with the pony engine concept. A small engine with it's own shaft and folding (for low drag when not in use - 99% of the time) prop....no rudder....Hummm? What are the statistics on steering failure? Auxiliary steering gear is of prime importance in the commercial boat and ship world......Again see the Marco Polo, two rudders (100% redundancy).

In my experience, if an engine is left to sit idle all it's life, it will fail when asked to operate under heavy load in some desperate situation.....So my take is that if you must have some redundancy, use it every day to be ready for that failure you know is coming.......This is why I conceived the use of smaller twin engines in my Passagemaker Lite series......Since the original we've gone smaller (the 39') with a single engine, to suit a particular client.

All my personal experience, including month long fishing trips offshore, have been in single (propulsion) engine boats. In thousands of hours and lots of breakdowns of various types, the only time I've been towed due to engine failure was with an old 60HP Mercury outboard when I was 17 years old.....

Tad Roberts said:

I guess I'm late to this....but there was a question to me specifically, somewhere a long ways back.......

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Thanks for your perspective, Tad.

This was the question from post #38:

"I'd love to hear Tad Roberts' perspective on the advantages, disadvantages, practicality and costs of protective bilge keels on twin recreational trawlers in the 30-45 foot range. I've often thought that they would provide the needed protection and roll stability on twin boats (like mine!!) that lack both. "

psneeld said:

Being an ACTUAL delivery captain...I would take whichever I was hired for...I've moved twins that never made it 100 yards to the fuel dock because the impellers had taken a set from 2 years on the hard...4 hrs later and I was still on my way...had it been a single..it would have been 3 hours and on my way.

Your question is idiotic...world class boats designed with one engine...ready and raring to go and you wouldn't go? I wouldn't either without tools and parts...but that would be the only reason.

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Relax Captain. The hypothetical question as well as this thread is just for fun. If you don't like it just ignore it.

So if the choice was yours which KK58 would you pick? I'm just teasin'.

FlyWright said:

Thanks for your perspective, Tad.

This was the question from post #38:

"I'd love to hear Tad Roberts' perspective on the advantages, disadvantages, practicality and costs of protective bilge keels on twin recreational trawlers in the 30-45 foot range. I've often thought that they would provide the needed protection and roll stability on twin boats (like mine!!) that lack both. "

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Fly....

I would refer to them as skegs rather than bilge keels which to my mind are something completely different. Advantages would be they provide the necessary prop/rudder protection, and as you mention some added roll damping and upright drying out. Main disadvantage is added drag and expense.

But it's really a problem if you have a typical mid engine type boat. Often they have a fairly shallow shaft angle and a lot of shaft is exposed below the hull (sometimes with two struts on each shaft). I believe some Grand Banks are this way. The fixed skeg then has to become really long to fully enclose the shaft, not practical. I have used them on the PL series boats (in conjunction with prop pockets) but that's using high shaft angles (which adds some loss) and vee drives.

The Great Harbor boats have twin engines with each prop protected by a skeg.

All the Grand Banks twin engine models except the new pod-drive boats have long shafts supported by one or two struts.

Tad Roberts said:

Fly....

I would refer to them as skegs rather than bilge keels which to my mind are something completely different. Advantages would be they provide the necessary prop/rudder protection, and as you mention some added roll damping and upright drying out. Main disadvantage is added drag and expense.

But it's really a problem if you have a typical mid engine type boat. Often they have a fairly shallow shaft angle and a lot of shaft is exposed below the hull (sometimes with two struts on each shaft). I believe some Grand Banks are this way. The fixed skeg then has to become really long to fully enclose the shaft, not practical. I have used them on the PL series boats (in conjunction with prop pockets) but that's using high shaft angles (which adds some loss) and vee drives.

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Thanks much for that reply. I really appreciate your perspective and contributions!

mahal said:

Relax Captain. The hypothetical question as well as this thread is just for fun. If you don't like it just ignore it.

So if the choice was yours which KK58 would you pick? I'm just teasin'.

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I AM relaxed...why in the world would you think I'm not?

I'm on a 4 month cruise till my work (if you can call it that) starts up again?

I wouldn't pick either if I had a choice...even for my own boat...as for doing it for a job???? Like I said...whichever I'm assigned and it's properly outfitted for the trip....

sunchaser said:

Bruce K said:

"Marin, just how do you do that, so that the undriven gearbox is not being turned by the prop?"

Bruce, many transmissions/gear boxes do just fine rotating on a "dead" engine. Our Hurth book says no problem trailing the prop, which we indeed have been forced to do with no overheat resulting. Your manual should specify if it is a problem.

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Interesting thought Tom. BW manual I previously downloaded for Velvet Drive 70C and 71C models (I have to check the plates on my transmissions the identifiers in my IG Manual are 10-13-000-003&4) has this:
"Freewheeling.
Under sail with the propeller turning, or at trolling speeds with one of 2 engines shut down, the design of the Velvet Drive gear maintains adequate cooling and lubrication"

Plenty of sailboats do 7 knots, an old trawler like mine should not exceed that on 1 engine. New Years Day I ran the boat after installing a thermostat in the port engine where there was none ( slow to warm, not reaching full temp),thinking it would be ok having renewed heat exchanger, oil cooler,and fixed the raw water pump. It overheated. At slower speed it was just ok, so I ran it only slowly going home. All was well next day with thermostat removed. Now the cause. New AD supplied thermostat came out dirty, maybe I need to flush the fresh water side, I`m yet to boil test the thermostat but doubt it`s at fault. Then query the fresh water pump.
Glad I had twins that day!

BruceK the identifiers in my IG Manual are 10-13-000-003&4) has this:
"Freewheeling.
Under sail with the propeller turning, or at trolling speeds with one of 2 engines shut down, the design of the Velvet Drive gear maintains adequate cooling and lubrication"

A while back there was an extensive discussion on what constituted 'trolling' speed, I think 3-4 knots was the agreed figure

What is the agreed-upon "under sail" speed? Many of my friends sail at 6-7 kts.

mahal said:

A hypothetical question to all: If you were employed as a captain by a Brokerage in Florida that needed to move one of their two new Krogen 58's to Costa Rica and the boss gave you the choice of either taking the one with twins or the single screw, which one would you pick?

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How much time do I have and who's paying for fuel?

New boat deliveries are tough because they can suffer from what I call SID (sudden infant death). If something is going to fail on a new boat or a new system, it seems to happen with in the first 30 days.

Now if you asked if someone was to give me a new Krogen 58 and I had my choice of engines, I'd take the single.

New boat deliveries are tough because they can suffer from what I call SID (sudden infant death).

You bet , after the first 500 hours , with book maint, the failure rate should be close to ZERO.

psneeld said:

I AM relaxed...why in the world would you think I'm not?

I'm on a 4 month cruise till my work (if you can call it that) starts up again?

I wouldn't pick either if I had a choice...even for my own boat...as for doing it for a job???? Like I said...whichever I'm assigned and it's properly outfitted for the trip....

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My bad Capt. When you called my game idiotic and refuse to give an answer, It gave me the impression that you were anything but relaxed.

Larry M said:

How much time do I have and who's paying for fuel?

New boat deliveries are tough because they can suffer from what I call SID (sudden infant death). If something is going to fail on a new boat or a new system, it seems to happen with in the first 30 days.

Now if you asked if someone was to give me a new Krogen 58 and I had my choice of engines, I'd take the single.

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Time is unlimited and fuel is provided by the dealer.

Larry, as a Krogen guy you probably know that even though the KK58 is offered in single and twin configuration, almost all of them are twins and the very rare singles come with a wing engine which I don't really consider a true single screw. But for this game, let's assume that the single is a true single screw.

I feel better with a back up power supply. It doesn't have to make sense. But I'd prefer something other than another of the same; just for interest. Back up sail power catches my interest. Really - it is difficult to accurately justify - go for whatever makes you feel at ease. How you maintain whatever you have makes more of a difference than what you have.

mahal said:

Time is unlimited and fuel is provided by the dealer.

Larry, as a Krogen guy you probably know that even though the KK58 is offered in single and twin configuration, almost all of them are twins and the very rare singles come with a wing engine which I don't really consider a true single screw. But for this game, let's assume that the single is a true single screw.

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A new boat delivery, sure I'd deliver the twin first but only because of SID and I don't know the boat. When I've done deliveries, I bring my own navigation system for the same reason.

As I said before though, I would take the single if someone were to give me one. What can I say, I'm a single kind of guy. If I wasn't, I never would have left Alaska.

Single malt scotch, single barrel bourbon, single engine boats. See a patern?

FlyWright said:

"I'd love to hear Tad Roberts' perspective on the advantages, disadvantages, practicality and costs of protective bilge keels on twin recreational trawlers in the 30-45 foot range. I've often thought that they would provide the needed protection and roll stability on twin boats (like mine!!) that lack both. "

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Years ago, I was cruising the Sea of Cortez with my brother on his 42' Californian Sport Fisher. We encountered a pod of Killer Whales (Yes...Killer Whales in the Gulf of California) which came up just behind the stern of the boat. We were doing about 10knts & the whales found this to be a nice speed to "play with the boat." One of them dove under the boat and hit the prop shaft on the port side, causing a severe vibration. We limped in to La Paz and had the shaft straightened. Years later, while on a fishing trip, a similar thing happened with a Humpback in SE Alaska. Although I've had 4 twin engine boats since 1995, the fact that those twin shafts hang out in the slip stream is constantly on my mind.

A skeg (an arm extending from the rear of the keel to support the rudder and protect the propeller) is also desirable.

Mahal-to my knowledge, the only KK 58 with a single engine is Hull #1, and I am pretty sure it does not have a wing engine. All the 58's since, are twins with the shafts fully enclosed in the skegs.

I have always thought the concept of a wing engine as on the Nordhavns was pretty silly. As was noted earlierby Tad, they are hardly capable of maintaining any speed or navigability in more than flat seas. The 57 Nord had a 62 hp Yanmar with a folding Sailprop in a 120,000 lb boat. If they have upsized them, maybe they are a bit more effective.

If you are a twin engine guy, and like Marin I am, at least have two real engines.

The 57 Nord had a 62 hp Yanmar with a folding Sailprop in a 120,000 lb boat. If they have upsized them, maybe they are a bit more effective.

One hp per ton will move the boat and get you home.Needs a better prop tho.

The big advantage is the vessel is operational and proceding under her own power , so a tow would not involve salvage.

I note that get home engines for recent vintage N55s are 70 HP and N62s are 80 HP. This is plenty of HP to get home. Few serious single engine MV blue water cruisers today are without a "big" get home setup. Dashew's single engine FPB 64 has a 7 knot get home.

The well heeled owners of these vessels are not persuaded to follow the mantra of the TF single engine only supporters. Those 1%ers march to a blue water risk averse drum, which is not necessarily how they became 1%ers.

sunchaser said:

I note that get home engines for recent vintage N55s are 70 HP and N62s are 80 HP. This is plenty of HP to get home. Few serious single engine MV blue water cruisers today are without a "big" get home setup. Dashew's single engine FPB 64 has a 7 knot get home.

The well heeled owners of these vessels are not persuaded to follow the mantra of the TF single engine only supporters. Those 1%ers march to a blue water risk averse drum, which is not necessarily how they became 1%ers.

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I'd love to know what that means and WHAT the "mantra" you have guessed from a few one liners to a short paragraph is of the TF single engine supporters....

The N57 I just did a delivery on had a 80hp wing with a rather large folding prop, it was off centerline about 4'and behind the main 10'. The Owner said it had a demonstrated ability to be able to push the boat at 4kts. The boat steered ok but docking would be tricky.. the thruster would be used to get the boat in in close quarters. The thing I liked about the 57 was the hydraulics could be ran from the wing engine, maneuvering was done with the wing engine at 2000 rpm to run the bow and stern thruster. This should help the wing to live a longer life as it gets used often and will not die due to non use.

Personally I think this is the only way to equip a passagemaker, true twins are more difficult to maintain due to space ( my current boat is a twin so I am not just hypothesizing ). The ease of maneuvering is good... but I could with confidence get the N57 with thruster in places I would not want to try to place my 45' SeaRay with twins. The access on the N57 for systems was fantastic ( except for the stbd stabilizer ). This N57 is slated to go around South America via Cape Horn in the future and I hope to be aboard as I have total confidence in its ability and system. ....I will send pics!
HOLLYWOOD

as a side note:
Every once in a while the Dashew boats are mentioned... While I give high regards to the Dashews for their voyages, sailboat designs, writing abilities, insights.. bla bla. bla.. I PERSONALLY think their power boats are not remotely pratical and have the at anchor use comparable to sitting on the top of a container (with the exception of I do like the aluminum part ). The Diesel Ducks also fall into this category. Now before some get their shorts in a knot. I am not saying that I think they are bad passage making designs... just that at anchor you perch on top of the deck like a bunch of rednecks on a motor home at a NASCAR race. Little thought was given to deck use at anchor.
Now that I have offended NASCAR fans, the Dashews, owners of Diesel Ducks, twin engine owners,
Happy New Year

Mark, that strut from the keel to the bottom of the rudder is usually called a "shoe".

I'm not sure the word "skeg" is applicable to the Krogen twins. It's my feeling/opinion that a skeg is a device devoted mostly or (usually) completely to directional stability as in the drop down fin aft in a kayak through a slot like a centerboard on a sailboat. Or a small or smallish keel/finlike extension along the center line of an OB well aft to (again) give the boat more directional stability. What are the little fins on racing OBs just aft of amidships called? Those boats would just slide sideways w/o them. They are undoubtably for directional stability and I think they are called skegs.

As to the big Krogen's keel-like things that carry the prop shafts ... I see no reason to call them anything other than keels. Much shorter than typical and not on CL but they perform the duties of a keel ... exclusively and completely in a dedicated manner. And if they were missing (open shafts as in a typical trawler) a keel in it's usual place would be necessary. If the Krogen's keel/skegs were w/o prop shafts, rudders and props they could, perhaps be called skegs I suppose but as built I see them as keels.


Re Tom's post I was a bit foggy as to his specific meaning but I'll bet he's refering to the misconception that one is safe as a bug in a rug w a single.
When you buy a trawler and don't shop till you drop in a quest to get a twin you'll probably wind up w a single. Without much thought too as it's not easy to "wind up" w a twin just as you won't wind up w a full disp hull trawler as there are even fewer of them than twin engined trawlers. So there are features of our boats that we didn't necessarily choose.

hollywood8118 said:

The thing I liked about the 57 was the hydraulics could be run from the wing engine, maneuvering was done with the wing engine at 2000 rpm to run the bow and stern thruster. This should help the wing to live a longer life as it gets used often and will not die due to non use.
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The ease of maneuvering is good... but I could with confidence get the N57 with thruster in places I would not want to try to place my 45' SeaRay with twins.

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I had the opportunity to cruise parts of B.C. years ago aboard my friend's 57 Nordy. I experienced the operation of the wing engine & bow thruster (run from the hydraulic system) and was most impressed. (The windlass was also run by this system.) However, I never gave the increased life expectancy of the "wing" any thought. You're right! It's a great set up.

My biggest gripe about the boat was when standing at the foot of the bed in the forward stateroom, I could not close the door (slider) without scraping my heels!

hollywood8118 said:

Personally I think this is the only way to Every once in a while the Dashew boats are mentioned... While I give high regards to the Dashews for their voyages, sailboat designs, writing abilities, insights.. bla bla. bla.. I PERSONALLY think their power boats are not remotely pratical and have the at anchor use comparable to sitting on the top of a container (with the exception of I do like the aluminum part ). The Diesel Ducks also fall into this category. Now before some get their shorts in a knot. I am not saying that I think they are bad passage making designs... just that at anchor you perch on top of the deck like a bunch of rednecks on a motor home at a NASCAR race. Little thought was given to deck use at anchor.
Now that I have offended NASCAR fans, the Dashews, owners of Diesel Ducks, twin engine owners,
Happy New Year

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Very true, the Dashew FPB 64 MVs are not designed to be superior dock queens. Their audience is a well heeled converted sail boater who has spent much time on blue water routes where dock queen niceties are not so nice. They are designed to take a roll over and come back up. With too much width and all the top heavy dock queen stuff so many of us like, recovery from a capsize would not be possible.

I find it interesting that much of the single Vs twin debate mentions the passagemakers. These are high availability single engine designs that have features like keel cooling, dry stack exhaust, and geared pump engines.

And, as its been mentioned they almost always have a "get home engine".

I find it ironic that most of the people arguing for single engine installations have boats that incorporate none of these high availability design features.

It seems that a great part of this argument is at least here on TF designed to justify to others (and possibly ourselves) what we already own.

Not meant to point fingers with that statement, I do my own justifying, in my own way. People have told me that my boat is a prissy dock queen, and a Bayliner to boot! I've justified my purchase by proving them wrong, simply by going pacces and doing things that they probably thought you need a Nordhavn for.

The single engine guys do the same thing every day. They go out in their boats and take them places that the twin engine crowd would cringe at, and they do it with full confidence in their engine. and you know what...

Just like me in my Bayliner, the single engine guys make it home safe and sound and wonder what all the fuss is about.