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Old 03-22-2017, 01:53 AM   #81
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Yes, but Brittanica, that was because in your sail boat it would have been a drive similar to outboard motors, with actual gears to mesh. That's the problem with what would otherwise be an easy solution for one of the issues at least, and if it stopped the shaft turning, the shaft seal issue as well, with boat gearboxes. These gearboxes are not meshing teeth like in a land vehicle with a manual tranny, but more like the auto tranny in automatic car gearbox, and need oil pressure to actually engage the drive in either direction, so I doubt it would work, as Nightsky has indicated. Unless the turning prop generated enough pressure to lock it up..? But then as soon as the prop stopped turning, you'd lose oil pressure and the locking effect and be back to square one, so I think not...
That's very interesting. I am barely two years into trawler ownership and wasn't aware how these transmissions work. Now I know!

Thanks

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Old 03-22-2017, 01:58 AM   #82
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Our primary reason for twins is simple. Power and performance. It's not redundancy, it's not handling. Those are all additional reasons but they don't even come into play in our decision making because we've already chosen twins to have the power.
you are right if you want to speed heavy board twins are justified.

When Article Rating realize you are a very narrow vision of subjective commercial vessels globally, you look at things from the perspective of Ameriikalaisesta and unfortunately the US is not all the world. Engine manufacturers will see the global and know their machines, users will certainly further and more objectively, as we are here, with all due respect to you.

I referred to the Maersk ship, for example. Emma Maersk is one of the main engine Finnish 1 × HSD-Wärtsilä-Sulzer RTA96-C diesel 80 080 kW speed 23 knots.

Should any single motor boaters who go to sea to put on top of assurance

Do not get me wrong the writing, not meant to offend, the purpose of that look more broadly, the rest of the world is considerably bigest than the US.



Security of supply and would recommend the Emma Maersk chief. because we have only a single diesel
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Old 03-22-2017, 03:06 AM   #83
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Security of supply and would recommend the Emma Maersk chief. because we have only a single diesel
Most of the newer Maersk ships are twin engines, even those with only a single prop and shaft. On the Emma Maersk, let's not overlook that in addition to the main engine of 109,000 hp, there are two 1200 hp electric motors augmenting it on the same propeller shaft.

If I had 109,000 hp, I'd probably forego having twins. lol
3,600 gallons of fuel per hour would be a challenge though.

Overall, I'm not sure the Emma Maersk at 1300'+ tells us much about what is appropriate for small recreational vessels.

There is one thing we can learn from it though. It uses a silicone based bottom paint instead of biocide type paints like most of us use. That is finding it's way into recreational vessels in Europe and there are those who predict that the bottom paints we currently use will be made obsolete by silicone. Life is projected at 8-10 years.
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Old 03-22-2017, 04:27 AM   #84
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Many of the luzzus in Malta have two engines, one offset, not twins, so that the seine doesn't get caught in the main drive.
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Old 03-22-2017, 11:04 AM   #85
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I have twins because I go way out in the Bahamas. If I never left the US, I would have a single for sure.
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Old 03-22-2017, 12:49 PM   #86
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I have spent over 30 years exploring underwater cave systems. In an eternally dark cold and deep environment, redundancy is the difference between walking out or getting bagged and dragged out. On dives where we used propulsion, even then we towed and staged multiple scooters. Never thumbed a dive due to having extra gear and never heard of an accident caused by the same.

I still enjoy going to remote locations and making my own charts, but my wife now insists I do it above ground. Fortunately a boat capable of doing that came along.

Helen Marie, I think Nils no doubt inspired Jeff Leishman on her design.

Nomad here's a couple more pix to alleviate the confusion.
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As Helen Marie observed she very much out of a lucander styled mould, one ballasted keel with two keel sized skegs and shaft brakes.
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Old 03-22-2017, 01:31 PM   #87
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Cafesport

A few years ago while negotiating on an N55 I had many conversations with owners and designer regarding the twin keel twin vs single with a get home. My take was the twin keel had about a 10% fuel penalty but with the get home removed and 2 smaller main engines the ER did not seem cramped at all. I also had designs for an aft cabin N52 with twin keeled JD 4045s. I still lament not pursuing that design and build further.

Owners of N55 twins reported the boat tracked marvelously in following seas. I'm sure you could add dozens of comments on single vs twin for the N 55.

Some years ago NT built a 52 in twins. The comparison to the same hulled single for costs, ER room and economy were written up in PM. No negatives as best I recall, remembering two smaller twins vs a much larger single can be attractive to many. Me for one. Many KK 52 owners too!
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Old 03-22-2017, 01:50 PM   #88
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I've been reading this thread with interest. Naturally it turned from a question about how it is to handle twins to one about twin vs single engines.

For my purchase decision it wasn't a key factor. I looked at a couple of twin engine boats before getting my single. The lack of a get home engine on my boat concerns me a little bit - though not too much for coastal cruising. At some point I plan to use my 20kW generator to power a get home motor. Either hydraulic or electric depending on which technology seems best at the time. This will be a necessity before I go on long passages away from towing services or cross oceans.
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Old 03-22-2017, 02:21 PM   #89
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Sunchaser, I just did a back to back delivery of sorts, one leg on a 62 and the next on a 60. Onboard was a fellow who owned a twin engine Krogen 58, a twin engined 55, a single engined 55 and a 57. It was interesting to compare notes.
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Old 03-22-2017, 02:31 PM   #90
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Sunchaser, I just did a back to back delivery of sorts, one leg on a 62 and the next on a 60. Onboard was a fellow who owned a twin engine Krogen 58, a twin engined 55, a single engined 55 and a 57. It was interesting to compare notes.
Yeah, interesting comparisons for sure. especially with most if not all Nordhavn twins and KKs having wet exhaust vs dry stack.
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Old 03-22-2017, 05:27 PM   #91
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Curious how many folks have really owned and/or spent large amounts of time with both a twin and single engine?

Good point. We ran our first larger boat, a single, for about five years. After that, twins. I'd go back to a single in a heartbeat... if that suited the boat, and our goals, at the time.

But I can't argue one or the other is better; pros and cons with each.


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Charter fishing boats in most areas are primarily twins. We just had someone here go fishing out of Westport WA. Tons of charter fishing boats there and nearly all are twin diesels.

That's interesting. I think most (almost all?) of the charter boats around here are singles, mostly diesel these days but many gassers are still in operation.

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Old 03-22-2017, 06:11 PM   #92
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Can't you just put the non functioning engine in gear? That's what I used to do on my sailboat - lock the transmission in reverse to prevent freewheeling while sailing.

Richard
Most all the transmissions used on our type of trawlers use oil pressure created on a pump attached to the input shaft (which connects to the engine) within the transmission to lock up clutch packs. (There are a few exceptions) If the engine isn't running, no oil pressure - shifting has no effect at all.

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Old 03-22-2017, 07:04 PM   #93
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If I had a twin, I'd never consider running them singly. If the boat was "right," there's little excuse to run only one unless the other was broken.
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Old 03-23-2017, 12:12 PM   #94
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I have twins in my 52 ft OA. Wonderful. Many times two engines were a savior.
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Old 03-23-2017, 01:03 PM   #95
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If I had a twin, I'd never consider running them singly. If the boat was "right," there's little excuse to run only one unless the other was broken.
Mark,
It's just to burn less fuel. And if you need to go to that extreme to save small amounts of fuel you've got ... the wrong boat.
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Old 03-23-2017, 01:17 PM   #96
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Once again nearsighted responses from lack of variety in boats and opareas.

There are places some twin engine boats can hardly go slow enough on one engine even in idle.

My last boat I trolled for fish all day long switching between engines one at a time just to keep them in operating temps and keep the hours down.

I thought that I would do the same through the endless no wake or slow speed zones encountered along the ACIW.

Another example where there are totally different requirements depending where you boat.
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Old 03-23-2017, 01:25 PM   #97
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Once again nearsighted responses from lack of variety in boats and opareas.

There are places some twin engine boats can hardly go slow enough on one engine even in idle.

My last boat I trolled for fish all day long switching between engines one at a time just to keep them in operating temps and keep the hours down.

I thought that I would do the same through the endless no wake or slow speed zones encountered along the ACIW.

Another example where there are totally different requirements depending where you boat.
The AICW no wake zones are easy compared to the Erie Canal. 4.3 knots is impossible with two engines in gear. However, as soon as we escaped the canals, speed was nice to have.
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Old 03-23-2017, 02:30 PM   #98
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The AICW no wake zones are easy compared to the Erie Canal. 4.3 knots is impossible with two engines in gear. However, as soon as we escaped the canals, speed was nice to have.
We have no problem going 4 knots on two engines. But then we have a purpose designed trawler.
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Old 03-23-2017, 02:54 PM   #99
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My last boat I trolled for fish all day long switching between engines one at a time just to keep them in operating temps and keep the hours down.
Did the same thing fishing inshore frequently on a twin engine sportfish without trolling valves, would occasionally have to switch engines just to make a turn but it worked fine. Fished on another boat for 1 day with twin I/O's and didn't think to check which engine ran the power steering pump and as luck would have it I shut down the wrong one. No harm or foul but it took me a couple of seconds to realize what I had done.
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Old 03-23-2017, 03:39 PM   #100
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If I had a twin, I'd never consider running them singly. If the boat was "right," there's little excuse to run only one unless the other was broken.
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Mark,
It's just to burn less fuel. And if you need to go to that extreme to save small amounts of fuel you've got ... the wrong boat.
Sometimes I get the feeling that both of you guys are blinded by your own perspectives. There are many legitimate reasons to run a twin on single engine. You just need to be able to see past your own blinders.

No sense beating a dead horse, though...only to be told I'm wrong or have the wrong boat.

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