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Old 01-27-2019, 10:25 AM   #1
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Understanding Engine HP??? Caterpillar vs Ford Lehman?

Hello,

We have been looking at used Trawlers at or around 40 Ft at or around $150k.

We have been leaning towards the Mainship 400 because is seems to fit our needs, both in budget and space....but I found a 1985 Kadey Krogen 42 that looks super nice, more room and its a Kadey!!!

But what I am confused about is the Mainship has a single Cat 380 HP diesel but the Kadey has a single Ford Lehman 135 HP...

What am i missing?? Why does the slightly smaller boat have so much more HP? Is it because is newer and engines are more advanced?

Thats over 3 times the HP....I guess there is something I am missing...

Comment welcome please...
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Old 01-27-2019, 10:36 AM   #2
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Hull shape.

That Mainship, with a semi displacement hull, and with that engine can get 16 knots.

The Kadey is a full displacement boat, once you hit displacement hull speed you start to push water - so not efficient. Hence you only need a smaller engine.

The Kadey's displacement hull speed is around 8.7 knots, assuming water line length of 42, which is probably less at 38/39. (1.34 X the square root of LWL).
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Old 01-27-2019, 10:55 AM   #3
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I suspect the kk42 might hit 8.7 at WOT. I suspect cruising speed to be closer to 7.8. However, at 7.8 I bet the boat is going better than 3kts per gallon.

I am sure Richard on dauntless can give us exact answers to this.
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Old 01-27-2019, 11:13 AM   #4
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Others will respond I'm sure, but hull type is one reason. The Kadey has a "full displacement" hull, similar to a sailboat. Typically, speed of any hull (known as hull speed) is a function of its waterline length,. Google "hull speed formula". A full displacement hull is seaworthy and very efficient but it's speed is limited to hull speed or very close to it. Generally speaking, it doesn't have a lifting component in its design so it can't get up "on plane" to increase speed above hull speed no matter how much horsepower the engine has. The Mainship hull its sometimes called modified planing and sometimes semi-dispacement. In any case, it has a lifting component & will plane or at least get partially up to allow a speed increase above hull speed, but it takes a bunch of power (and fuel) to do it. The Krogen hull is very seaworthy and KK42's can and have crossed oceans. The Mainship is a capable boat, but is a bit more "tender" in open water. So which boat? Depends on where you plan to travel with her. Like I said, I'm sure others will chime in.
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Old 01-27-2019, 11:51 AM   #5
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Only a handfull of FD trawlers here on TF.

Most all are SD as people are accustomed to the large engines of planing craft but more importantly speed. Visualize ... my boat (30’ 8 ton) in a boat show. Man says I like that boat. What engine she have? The salesman says 37hp 4 cyl. The man is astonished. NO... WAY I’m going to look at that one over there. It’s got about 100hp.
And the next guy comes along and asks “how fast is that boat”. The salesman says “six or 7 knots”. Guy says “hey I can almost walk that fast”. I’m going over and look at that other boat. Looks more like a speedboat.

Nothing’s really changed. FD (slow) boats aren’t any more in demand than SD. People still like speed and power. Just like the cars of the 60’s and 70’s. And interestingly most Trawler owners grew up in the 60’s or 70’s. And my Avalon has closer to 300hp than 200hp. It’s nuts. The Toyota Camry 4 cyl engine would have plenty of power for the Avalon but no ... it gets 277hp. Can still hear the kid say’in “betcha my dad’s Merc can go faster than your dads wimpy Pontiac”.

But in Trawlers there is the weekend component. Lots of space out there and so little time.
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Old 01-27-2019, 02:54 PM   #6
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I have the slowest boat in our club, and that includes dinghies and, I suspect, most of the sailboats.
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Old 01-27-2019, 03:03 PM   #7
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Yes, most of our boats are not full displacement trawlers but rather semi displacement which can use the extra horsepower to go faster. Full displacement boats like the KK 42 do not benefit from more horsepower. Add a lot more power to the KK and it will make a big wake and burn a bunch more fuel and go slightly faster. FD boats need X amount of HP and a bit more for wind and current. X HP isn’t as much as you might think for a FD boat. On the other hand a semi displacement boat can use quite a bit of power. My boat model was built with twin 120s up to twin 275s because it is a semi displacement hull. With the 120s it is operated similar to a FD hull. With the larger power it can be run up almost on plane, just uses a whole lot more fuel.
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Old 01-27-2019, 03:48 PM   #8
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Quote:
Originally Posted by jefndeb View Post
Hello,

We have been looking at used Trawlers at or around 40 Ft at or around $150k.

We have been leaning towards the Mainship 400 because is seems to fit our needs, both in budget and space....but I found a 1985 Kadey Krogen 42 that looks super nice, more room and its a Kadey!!!

But what I am confused about is the Mainship has a single Cat 380 HP diesel but the Kadey has a single Ford Lehman 135 HP...

What am i missing?? Why does the slightly smaller boat have so much more HP? Is it because is newer and engines are more advanced?

Thats over 3 times the HP....I guess there is something I am missing...

Comment welcome please...
The Mainship has the 380hp so they can say it has a top speed of 16kts which sounds really great. The reality is that the fuel mileage at 16kts is so poor that nobody except the rich would run it at that speed for any length of time. We're talking .7mpg vs 2-3mpg. If one only runs a few miles to the sand bar and back, 16kts is great. For anybody doing long range cruising, the .7mpg is prohibitive.

The KK has a much more realistic HP that is very adequate for the type of use the boat was intended.

Keep in mind that most trawlers in the 4x' range need only about 60hp to run at 6-8mph which is the speed range that most are run at.

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Old 01-27-2019, 04:38 PM   #9
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OK, so basically since a full displacement type hull cannot get on plane due to its design, an engine that has less HP is sufficient to push through water were as a Semi Displacement hull that can partially get up on plane needs this extra HP to get up on plain although its not very fuel efficient to do so..do I have this right?
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Old 01-27-2019, 04:41 PM   #10
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Yes
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Old 01-27-2019, 04:50 PM   #11
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The boat in our avatar is a 38' full displacement hull. We run between Toronto and Abacos at 7knots using 0.75gph with a 55hp diesel. We can force 8knots but fuel useage triples (at least) and it get noisy ..... Thats the difference in a nutshell.
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Old 01-27-2019, 05:18 PM   #12
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Originally Posted by jefndeb View Post
OK, so basically since a full displacement type hull cannot get on plane due to its design, an engine that has less HP is sufficient to push through water were as a Semi Displacement hull that can partially get up on plane needs this extra HP to get up on plain although its not very fuel efficient to do so..do I have this right?
However that semi displacement hull can also be run at hull speed with very low HP. Grand Banks trawler is an example of a semi displacement hull that can be equipped with a low HP engine designed to be run at 7-8 kts or twin high hp Cats To get it up on plane......using lots of HP and fuel.
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Old 01-27-2019, 05:29 PM   #13
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Is it just me or is this an unbelievably beautiful boat....good price as well!!

View Yacht - Kadey-Krogen Yachts, Inc. : Kadey-Krogen Yachts, Inc.
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Old 01-27-2019, 06:25 PM   #14
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Very nice looking boat. good luck.
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Old 01-27-2019, 06:30 PM   #15
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Is it just me or is this an unbelievably beautiful boat....good price as well!!

View Yacht - Kadey-Krogen Yachts, Inc. : Kadey-Krogen Yachts, Inc.
It is but, and I may be having a old man brain fart, but I think that boat has been for sale for a while.

So, if you are interested, you need to wonder why.
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Old 01-27-2019, 07:36 PM   #16
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Too much teak decking for this sailor... but then again, I'm getting lazy in my old age...
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Old 01-27-2019, 09:11 PM   #17
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But...

Quote:
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Is it just me or is this an unbelievably beautiful boat....good price as well!!

View Yacht - Kadey-Krogen Yachts, Inc. : Kadey-Krogen Yachts, Inc.
You should talk to current Kady Krogan owners to discuss how the boat will perform without stabilizers. I have been on A 48 and could not imagine having one without stabilization. Some owners complain that they even roll too much when at anchor.

Gordon
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Old 01-27-2019, 09:22 PM   #18
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I am recaulking my teak sundeck this winter. Never again. A good friend had a full displacement Defever. We could not sit aboard it for more than a half hour due to the motion, my wife would start getting ill.
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Old 01-27-2019, 09:38 PM   #19
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The boat in our avatar is a 38' full displacement hull. We run between Toronto and Abacos at 7knots using 0.75gph with a 55hp diesel. We can force 8knots but fuel useage triples (at least) and it get noisy ..... Thats the difference in a nutshell.
Wifey B: And the boat currently in our avatar is 44' planing hull. We run between Key West and Daytona and sometimes the Bahamas at 35-37 knots averaging 0.66 nmpg with twin 800 hp diesels. We can force 42 knots. Not as noisy as you might think as 74-75 decibels at cruise.

In a nutshell it's all very different type boats for different uses. Now we have a boat we cruise slower and further in but nothing that is full displacement or truly close to a trawler. You have to figure out what your need and desires are and match the boat to them.
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Old 01-28-2019, 12:58 AM   #20
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I am recaulking my teak sundeck this winter. Never again. A good friend had a full displacement Defever. We could not sit aboard it for more than a half hour due to the motion, my wife would start getting ill.
Geez, we've owned our DeFever 44 for five years, lived aboard for over two years, are presently 4,000 miles into a Great Loop cruise and have had no problem with the "excessive" motion you describe. In fact, we have found it to be quite stable. Yours is the first time I have ever heard a complaint of this type about a DeFever.
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