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Old 12-21-2018, 09:14 PM   #101
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Here is a "cold side" turbo temp at full load in 55* air. In a high ambient temp. over 400* is normal.



Attachment 83597



Just curious. Is the exhaust side coolant jacketed, or is it dry? And if dry, is it insulated?


I don't recall the exact temp, but the compressor side of my last boat's turbo, and the air pipe leading to the aftercooler were consistently the hottest parts of the engine. That makes sense, and I suspect is one of the things to causes some variation in radiated heat with power load, even though across the power range the coolant and block temp is tightly regulated and so would not put off appreciably more heat.
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Old 12-21-2018, 10:17 PM   #102
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Just curious. Is the exhaust side coolant jacketed, or is it dry? And if dry, is it insulated?


I don't recall the exact temp, but the compressor side of my last boat's turbo, and the air pipe leading to the aftercooler were consistently the hottest parts of the engine. That makes sense, and I suspect is one of the things to causes some variation in radiated heat with power load, even though across the power range the coolant and block temp is tightly regulated and so would not put off appreciably more heat.

Dry exhaust system.


This was on a land based emergency gen. But you're thinking is on the money. The cold side of the turbo will vary greatly with load. And can add a significant amount of radiant heat depending on how much surface area there is before it goes through the aftercooler. The engine block/heads will usually remain fairly consistent.
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Old 02-10-2019, 11:16 AM   #103
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Exhaust

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Good comparison.

So whatís the difference, you might ask? Well, since you asked, the difference is whether the work is conducted from inside the boat where it is warm and dry, or in the water where it is cold and wet. Iíll leave it to you to decide. You know where I landed on the question.
Great thread which I just read (second time) from start to finish. Enjoying your decision and equipment selection process. Regarding engine exhaust I have to agree with your observations and also notice a lower ER temperature with the sea water cooled exhaust. For what its worth I like our Cummins QSB for a number of reasons and wouldn't hesitate using another Cummins engine on our next boat. Keep the updates coming.

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Old 02-11-2019, 12:05 PM   #104
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Stabilization

Curious if you are selecting Trac Active Fin stabilizers or ?? on our N40's we had both Niad and Trac and prefer Trac. I noticed most new builds are still installing Trac systems and staying away from Gyro systems. Is this also your understanding ?

JT
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Old 02-16-2019, 01:04 PM   #105
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Displacement

TT, here is a question I hope you can assist me with. I continuously struggle with determining the "next step" required to truly appreciate the "feel" in a larger boat. I recall taking out a N47 while owning the N40 and being surprised how similar it felt to the N40. I recall telling Jeff Merrill, wow this doesn't feel much different despite the heavier displacement and longer waterline.

Going the other direction I do remember feeling the difference between the N40 and H38 which I contribute to displacement and hull shape.

Appreciate your thoughts. Thanks

John T
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Old 02-16-2019, 01:49 PM   #106
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Curious if you are selecting Trac Active Fin stabilizers or ?? on our N40's we had both Niad and Trac and prefer Trac. I noticed most new builds are still installing Trac systems and staying away from Gyro systems. Is this also your understanding ?

JT
I'm not sure it's possible to even figure out the trends on stabilizers right now as they vary so from boat to boat, builder to builder. In larger semi-displacement and planing hulls I'm seeing Gyro's dominating, but is it fad or trend? I have no idea. However, what I'm seeing a lot of now in larger boats, is both. Boats that one had Naiad standard now have Seakeeper and Naiad. On our Sunseeker, we had Sidepower/Sleipner Vector fins. They were incredible and perfect for that boat, but that's the exact type boat they were designed for and have been most tested on.

What it all says to me is that like everything else the stabilizers need to be matched to the boat and it's use. I'd tend to go with what the builder has used successfully. Then I'd also look at my needs. Are they needed for anchoring or underway the most or both equally. Which am I willing to compromise on.
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Old 02-16-2019, 02:05 PM   #107
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Originally Posted by N4061 View Post
TT, here is a question I hope you can assist me with. I continuously struggle with determining the "next step" required to truly appreciate the "feel" in a larger boat. I recall taking out a N47 while owning the N40 and being surprised how similar it felt to the N40. I recall telling Jeff Merrill, wow this doesn't feel much different despite the heavier displacement and longer waterline.

Going the other direction I do remember feeling the difference between the N40 and H38 which I contribute to displacement and hull shape.

Appreciate your thoughts. Thanks

John T
I think boat families share feel a lot of the time. I would expect the larger Helmsman to feel much more like your H38 than any Nordhavn or other brands. I've handled a 44' and 63' from the same builder and from the helm seat to high speed handling, you knew they were related and I've handled an 85' and 130' from the same builder and the 85' simply felt like a smaller version of the 130'.

Good builders find something they're good at and they do it over and over. They introduce other boats and even restyle but the genetics don't change.
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Old 02-16-2019, 02:13 PM   #108
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Your comments on the coolant pump leaks on the JD 6090 I find interesting. It has been an issue on some 6068s as well. Did Lugger have a different marinization design for the coolant pump in the "old days?"

One of the things I really like about our Perkins Sabre 225s/Cat 3056s is the great access to all cooling system components. When one of our coolant pumps started dripping I did a little research. The seal is a ceramic/carbon design and can pick up a small speck of dirt that causes an uneven spin and eventual cracking. Dirty coolant was suspected - that suggests on a keel cooled large liquid capacity setup maybe an inline coolant filter would be helpful. The drip was slight but worrisome so the coolant pump was changed out, quite easily I might add.

So if looking for any suggestions, maybe a coolant filter would be in order for your wet exhaust design. I've seen them on Scania non marine engines, whether OEM of after market I don't know.
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Old 02-16-2019, 07:09 PM   #109
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Boat Similarities

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I think boat families share feel a lot of the time. I would expect the larger Helmsman to feel much more like your H38 than any Nordhavn or other brands. I've handled a 44' and 63' from the same builder and from the helm seat to high speed handling, you knew they were related and I've handled an 85' and 130' from the same builder and the 85' simply felt like a smaller version of the 130'.

Good builders find something they're good at and they do it over and over. They introduce other boats and even restyle but the genetics don't change.
Excellent point, and I agree. My limited time aboard Kadey Krogens confirm similar boats have similar feels. While the Nordhavns push water aside the KK and Helmsman have a cleaner entry and you can feel the difference. Not much difference between KK 39 and KK 44.
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Old 02-17-2019, 06:58 AM   #110
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Curious if you are selecting Trac Active Fin stabilizers or ?? on our N40's we had both Niad and Trac and prefer Trac. I noticed most new builds are still installing Trac systems and staying away from Gyro systems. Is this also your understanding ?

JT

Yes, the stabilizers are ABT fins, including at-rest stabilization. In fact, the entire hydraulics package is ABT. The other components are the windless, 40hp bow and stern thrusters, anchor wash pump, and 180 gpm (10,800 gph) emergency bilge pump. I think ABT is one of the Gold Standards in the marine industry for engineering, quality, and support.


I know of one Nordhavn 63 that was build with gyros, and never heard any reports of performance. I think they might have build a Coastal Pilot with one too, but am not certain.
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Old 02-17-2019, 07:24 AM   #111
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Originally Posted by N4061 View Post
TT, here is a question I hope you can assist me with. I continuously struggle with determining the "next step" required to truly appreciate the "feel" in a larger boat. I recall taking out a N47 while owning the N40 and being surprised how similar it felt to the N40. I recall telling Jeff Merrill, wow this doesn't feel much different despite the heavier displacement and longer waterline.

Going the other direction I do remember feeling the difference between the N40 and H38 which I contribute to displacement and hull shape.

Appreciate your thoughts. Thanks

John T

In all honesty I'm not a good person to answer that, or at least I only have limited experience to answer it from. I think it's something many of us struggle with because we don't spend extended time cruising is a variety of boats. Here are the few observations that I have from the boats I've owned.


- A planing hull has a much snappier roll to it. This makes sense because the flat bottom wants to follow the sea surface. A displacement hull roll much more slowly, influenced by the sea surface, but not totally controlled by it like a planing hull.


- When planing, a planing hull becomes very stable, and the motion in head seas is a bump bump bump. At displacement speeds, planing and displacement hull alike follow head seas up and down and you get pitching rather than bump bump bump. Personally I find the pitching to be the most objectionable, and ultimately nauseating.


- As boats get bigger, it just takes bigger seas to make it move around, but it still moves around the same way, though perhaps slower.


Not sure if that helps.
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Old 02-17-2019, 07:36 AM   #112
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Peter
Your comments on the coolant pump leaks on the JD 6090 I find interesting. It has been an issue on some 6068s as well. Did Lugger have a different marinization design for the coolant pump in the "old days?"

I don't think Lugger changed the coolant pump. I think they changed manifolds, heat exchangers, and turbo, and maybe the raw water pump. But I think the rest of the engine core was stock Deere.


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One of the things I really like about our Perkins Sabre 225s/Cat 3056s is the great access to all cooling system components. When one of our coolant pumps started dripping I did a little research. The seal is a ceramic/carbon design and can pick up a small speck of dirt that causes an uneven spin and eventual cracking. Dirty coolant was suspected - that suggests on a keel cooled large liquid capacity setup maybe an inline coolant filter would be helpful. The drip was slight but worrisome so the coolant pump was changed out, quite easily I might add.

I'm pretty sure the 6090 pump seals are lip seals. I've seen the ceramic seals in raw water pumps, but didn't know they were also used in coolant pumps. Learn something new every day.


Very interesting theory on dirt/contamination, by the way. I never though of that, and it would certainly explain things. The coolant that I drained was never visually contaminated, but that doesn't mean there still wasn't stuff in it. But there could easily have been construction dust and debris in there, even after a full coolant change which was done after the first replacement. If I still had the boat, I would pursue this theory for sure. Perhaps a fluid analysis...



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So if looking for any suggestions, maybe a coolant filter would be in order for your wet exhaust design. I've seen them on Scania non marine engines, whether OEM of after market I don't know.

I'll have to check to see if there is one. I don't recall seeing one. I know the QSM11 had one.
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