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Old 12-31-2012, 03:17 AM   #41
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I have said before that, given the reliability of today's diesels, I think the single v. twin has come down to personal preference. That said, on the KK 58, both shafts are protected by keels. The centerline keel sort of "fades" out at about 75% of the boat length and the twin keels start at about 60% of the length. Both shafts, props and rudders are fully protected. The added advantage of this design is that the boat can sit on her own bottom should that become neecessary (or unavoidable). I personally prefer twins and have had twins in 3 different boats. Fortunately, the engines and the engine room on the KK are well designed and access for any maintenance issue on either side of the engine is not an issue.
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Old 12-31-2012, 06:44 AM   #42
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The added advantage of this design is that the boat can sit on her own bottom should that become neecessary (or unavoidable)

Sounds like a British boat where "taking the ground" is a daily situation.

To my mind every inshore cruisers boat should be built with this in mind.
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Old 12-31-2012, 10:05 AM   #43
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I love this discussion! When I bought the Bristol, with it's single screw and huge keel, I had been looking for a long time. I've owned twins my whole life, but like most...my boating is a few days off each week and my wife and I must return to reality and go back to work, so we needed the speed and redundancy of a twin. I could not tell the
Chief Pilot we were stuck in Provincetown waiting for parts, so a gas gobbling planing hull with twins filled the bill. When we retire in 4 years, that bill will be filled with the Bristol; slow turning Lugger for fuel economy and range; big keel for protection of the running gear; massive amount of engine room around the diesel to work on it like a gentelman, thus keeping it tip top; the best fuel delivery and polishing sustem I could find; and a HUGE bow thruster up front to make me look like I know how to drive a single. Yes, reduntant engines whether in boats or airplanes are obviously better but for ONLY one reason...to keep moving! If one is not time constrained by a job, or in a hurry to get somewhere then back to the docks, or in horrific weather, (with today's modern wx reporting via i-pad or satellite, you shouldn't be) and you stay within seatow's range with good insurance, then a single will do the job nicely. Robert Beebe went across the Atlantic on a single quite a few times as do hundreds and hundreds of large, single engine commercial freighters every day. I have never had an actual "engine" failure, rather, the hoses, belts, etc. that are attached to them have failed. All easy fixes. Throw out a sea anchor, let the wife maintain the watch, and get down in that big engine room and change the belt! lol My coffee is finished so I'll sign off from my editorial. Thanks Mark for pulling the pin!
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Old 12-31-2012, 10:13 AM   #44
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Simply being able to maintain control of the boat and be able to move to an anchorage or come home on a remaining engine are my biggest reasons.

With twins... you have decisions that can be made. With a single you have a phone number: 1 (877) 844 5160
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Old 12-31-2012, 11:09 AM   #45
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Marin I want to see you doing your "walk in the park" and you can take your dog w you. The image would be more fitting that way. On a leash of course.
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Old 12-31-2012, 11:25 AM   #46
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Simply being able to maintain control of the boat and be able to move to an anchorage or come home on a remaining engine are my biggest reasons.

With twins... you have decisions that can be made. With a single you have a phone number: 1 (877) 844 5160
Utter nonsense...plenty of situations with even a single and you can keep moving.

I just had a high pressure fuel leak on an external injector feed in the more remote, narrow part of the Intracoastal.

I made it the next 20 miles to a safe haven (where I planned to be overnight anyhow) all the while driving through severe thunderstorms and a tonado watch....safely and without damaging anything....all without anchoring or calling tha number. I also have a VERY inexperienced crew so I had to navigate too.

Maybe some twin drivers need to learn more about dealing with emergencies than thinking 2 is better.

Marin has about the only answer I really accept...he likes driving a twin and that can't be argued with..
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Old 12-31-2012, 11:32 AM   #47
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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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Old 12-31-2012, 12:17 PM   #48
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More than a single didn't help these guys!


The Kulluk lost its towline from the Aiviq on Thursday. A second towline was attached for a time, but then early Friday all four engines on the Aiviq failed.
Shell Oil drilling vessel is adrift in Gulf of Alaska | McClatchy
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Old 12-31-2012, 12:33 PM   #49
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Utter nonsense...plenty of situations with even a single and you can keep moving.
Sure. But like we have both said many times, I can shut mine down instantly and still keep moving.

I actually did that yesterday while out just to see what would happen. I took my starboard motor out of gear, and shut it down. The autopilot corrected and I lost about a knot of speed. Just for giggles I went below and checked everything while the wife watched the helm.

The starboard shaft was free wheeling at about half the RPM of the running motor and I checked the oil and came back upstairs and brought it back online. It's a huge degree of redundancy and a wonderful plus in maneuverability, reliability and safety.
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Old 12-31-2012, 12:34 PM   #50
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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.
And a simple cross connect of cooling lines can take care of the cutless bearing water supply...might need to add check valves and slightly larger orifice at the feed sources.
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Old 12-31-2012, 12:44 PM   #51
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According to OC Diver twin owners are less diligent

According to Larry H big twin yacht owners like to run over logs

According to psneeld twin drivers need to learn more about maintenance

According to Mark his single purchase was the smartest decision made in the Bay Area since Alcatraz was closed

Wow, some real here.
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Old 12-31-2012, 01:22 PM   #52
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According to OC Diver twin owners are less diligent

According to Larry H big twin yacht owners like to run over logs

According to psneeld twin drivers need to learn more about maintenance

According to Mark his single purchase was the smartest decision made in the Bay Area since Alcatraz was closed

Wow, some real here.
Great boaters? You bet!

Plus I said dealing with emergencies...not maintenance... so add reading classes for twin drivers too...
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Old 12-31-2012, 01:54 PM   #53
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We all understand the concept of redundancy.

Eliminating single points of failure in any piece of equipment has proven itself to decrease outage time. This isn't even arguable, its just a fact.

Excepting for the potential issue of a single protected prop being less likely to sustain damage during a collision, there is zero logical augument that will support the same, or as some would claim increased reliability in a single engine installation vs dual engines.

There are alot of reasons one might prefer a single over a twin engine configuration, but reliability isn't one of them.
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Old 12-31-2012, 02:20 PM   #54
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... There are alot of reasons one might prefer a single over a twin engine configuration, but ...
With singles:

Lower acquisition cost.

Nearly half the engine and running-gear maintenance cost.

With half the engine and drive-train components, half the chance of something breaking/failing.

Shaft and propeller more likely to be better protected.

Engine compartment takes less space and/or is less cramped; accessibility likely to be better.

With two engines:

Something breaking/failing is much less likely to completely disable or shut down boat.

More likely capable of planing speeds.

Greater ease in slow-speed maneuvering.

The feel of adjacent dual throttle controls and reverberation of multiple engines so loved by multi-engine aircraft pilots and fans.
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Old 12-31-2012, 04:23 PM   #55
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Mark! It's about time you spoke up! And I see there are some fellow pilots in here. I've been flying over the Atlantic and Pacific for a long time and the old days of jets having wet footprints are long gone thankfully. Plus no seatow 8 miles up lol.
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Old 12-31-2012, 04:30 PM   #56
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With singles:

Lower acquisition cost.

Nearly half the engine and running-gear maintenance cost.

With half the engine and drive-train components, half the chance of something breaking/failing.

Shaft and propeller more likely to be better protected.

Engine compartment takes less space and/or is less cramped; accessibility likely to be better.

With two engines:

Something breaking/failing is much less likely to completely disable or shut down boat.

More likely capable of planing speeds.

Greater ease in slow-speed maneuvering.

The feel of adjacent dual throttle controls and reverberation of multiple engines so loved by multi-engine aircraft pilots and fans.

OK, now you've gotten somewhere.

There are things you can do to improve an engines Mean Time Between Failure (MTBF).

To reduce the MTBF you could:

Use a Naturally Aspirated engine
Utilize dry exhaust and keel cooling
Use an engine with no external oil lines
Use an engine with no belts

For me personally a single engine boat utilizing those types of systems would make single engine boating quite palletable.
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Old 01-01-2013, 12:18 AM   #57
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To reduce the MTBF you could:

Use a Naturally Aspirated engine
Utilize dry exhaust and keel cooling
Use an engine with no external oil lines
Use an engine with no belts

For me personally a single engine boat utilizing those types of systems would make single engine boating quite palletable.

Couldn't agree more.
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Old 01-01-2013, 12:46 AM   #58
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Well that settles it. Singles are better than twins. Discussion over. Everybody can go home now.
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Old 01-01-2013, 06:34 AM   #59
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A big advantage might be if the noisemaker and engine were identical, or at least identical maker.

A 6-71 for power and a 3-71 noisemaker would allow for a huge spare parts inventory.

Drop a valve and the noisemaker has a new functioning cylinder head, or a replacement exhaust manifold.

Also would reduce the spare parts purchase inventory.
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Old 01-01-2013, 09:48 AM   #60
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One of the things greatly favoring single engine installations is a reduced Mean Time To Repair (MTTR).

Much lower MTTR is acheived through easier access to the engine for repairs. This makes repairs much faster when a failure occures.
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