40 something foot yachts - engine variables

[Action]

In looking at "trawler" yachts for sale there seems to be a fairly wide range of engine HP choices. Not that one has a lot of choice in the used boat market.

What I don't exactly understand is twin engine HP ranges from 300 to maybe 800+. And I assume most of these hulls are semi-displacement hulls.

What possible use is 700hp twins in say a 42' aft cabin?
To move that type of yacht 8 to 10 kts, isn't 500 hp or less sufficient?

 

[mvweebles]

The argument for bigger engines is you can always go slow, but if you want to go fast, bigger is better. I'm not a fan of that, but there is a logic to that thinking.

500hp is 5x what is needed to do 8-9 kts. Back in the early days, a not-so-popular option for a Grand Banks 42 was a single 120hp Ford Lehman. It would easily move the boat at 8.5-9.0 kts. Fast forward 30-years and many were equipped with over 600hp combined and would do 18-20 kts.

New buyers frequently select the upgraded engines. So there are relatively few smaller engine examples on the used market. Guessing it's a remnant from auto-purchases where smaller engines are often offered to keep the price down, but it behooves a buyer to get the larger engine.

Even the Nordic/American Tugs have pretty large engines. Heck, a popular opion on the Willard 36 was a 135hp 6-cylinder Perkins, an 'upgrade' from the perfectly matched 4-cyl 75hp. Maybe it's something with Americans. "No substitute for displacement" as the old saying goes.

Peter

 

[Action]

Thanks for the feedback.

When I do pull the trigger, my use will be coastal and/or inland. With going slow or slower and traveling at some distance being the goal. Moving 10 or 20 tons of plastic in a go fast manner does not fit for me.

The newer the yacht it seems the larger the displacement of the engines. I am not exactly a fan of that either. I can get "go fast" in my Express Cruiser if I want that.

Wouldn't larger or higher HP diesel engines operated at low speeds be an issue for that large of an engine?

 

[RT Firefly]

Greetings,
Mr. mv. Go big or go home...

 

[kthoennes]

I don't know, I've got 500 or 600 horsepower and my boat is still a pig. But I don't mind.

 

[Comodave]

The first decision is to decide what cruising speed you want. It is easy to get 8 knots or so. But if you want 10 or a bit more then you will need more horsepower. If you are happy at 8 knots or less then the 120 horsepower is fine. You can always run larger engines slower but smaller engines can only run so fast. It may not be good for the larger engines to run slower but it does give the option to run faster.

 

[Delta Riverat]

My 21 ton 44 footer is equipped with (2) Volvo 235 HP turbo diesels. The engine manual advises "avoid prolonged operation under load below 1400 rpm"

At 1400 she does hull speed, 8 knots, cool.

At 1600 she will do 9-10 and the engines seem to like this speed, run smooth.

Flat out, 2650, she does 13, makes a lot of noise, makes white vapor out the exhaust and churns up a big frothy hump of water at the transom. Me thinks the props are cavitating. Big waste of fuel for not much extra. But broker advised this from time to time (blow the carbon I guess) and the next time I started the engines cold there was no black smoke at all. So me thinks he was right.

So I run the motors at 1400 to 1650 when cruising, 650 to 750 through no wake zones and flat out for 5 minutes once a year -

 

[RT Firefly]

Greetings,
Mr. DR. 5 minutes once a year? You rebel, you!

 

[Delta Riverat]

Hehe, Yeah Baby!

I like 1600. Smooth and nice. Flat out with all that froth and water vapor. A little scary -

 

[Action]

Hehe, Yeah Baby!

I like 1600. .....

... and I cannot lie.

Delta Riverat aka Sir boats-a-lot

 

[Lepke]

What possible use is 700hp twins in say a 42' aft cabin?

To go fast, get up on plane. Usually a sport fishing boat. Some people want to go fast and can afford the fuel expense. Everybody enjoys the water differently.

 

[ranger58sb]

In looking at "trawler" yachts for sale there seems to be a fairly wide range of engine HP choices. Not that one has a lot of choice in the used boat market.

What I don't exactly understand is twin engine HP ranges from 300 to maybe 800+. And I assume most of these hulls are semi-displacement hulls.

What possible use is 700hp twins in say a 42' aft cabin?
To move that type of yacht 8 to 10 kts, isn't 500 hp or less sufficient?

Yep, you get to choose -- from what's available.

You're talking total HP, yes? Not twin 800s or 700s or whatever, right?

Latter would be in a boat more like ours (twin 900s), planing hull, and 30-kt speeds...

I'd guess total HP in the neighborhood of 800 or so, in a 45'-ish semi-displacement boat, maybe a heavy build, might have been based on an assumption about occasional weather avoidance or some such. And the engines might have been what was available to the builder at a price point... and might have been just the next size up from other available but less capable engines (relative to that weather assumption).

-Chris

 

[Don L]

In looking at "trawler" yachts for sale there seems to be a fairly wide range of engine HP choices. Not that one has a lot of choice in the used boat market.

What I don't exactly understand is twin engine HP ranges from 300 to maybe 800+. And I assume most of these hulls are semi-displacement hulls.

What possible use is 700hp twins in say a 42' aft cabin?
To move that type of yacht 8 to 10 kts, isn't 500 hp or less sufficient?

I feel you!

 

[Iggy]

Personally, I do like the idea of a bigger engine. On my 40' trawler I do 8 knots running at 1700RPMs with a 350HP engine. If the engine was small it would work harder to do the same speed. Maybe even use more fuel?

On the other hand? Diesels like to run with a 75 to 80% load. From Delta ". The engine manual advises "avoid prolonged operation under load below 1400 rpm" Maybe going big is not a good thing? I don't know enough about it, but its a good question.

 

[Bmarler]

Personally, I do like the idea of a bigger engine. On my 40' trawler I do 8 knots running at 1700RPMs with a 350HP engine. If the engine was small it would work harder to do the same speed. Maybe even use more fuel?

On the other hand? Diesels like to run with a 75 to 80% load. From Delta ". The engine manual advises "avoid prolonged operation under load below 1400 rpm" Maybe going big is not a good thing? I don't know enough about it, but its a good question.

I have a 40 foot full displacement hull and 1700 gives me between 7 and 8 knots depending on conditions. I do it with less then half of your horsepower and zero laboring from the engine. At that rpm I’m burning a bit less than 2gph.

 

[Action]

Yep, you get to choose -- from what's available.

You're talking total HP, yes? Not twin 800s or 700s or whatever, right?


-Chris

I get to choose base on what is available on the market. Not on a "let's build this" basis.

Yes total HP.
In the world called perfect, I would build with a single diesel. Maybe two to three hundred hp. That power choice is more possible in pre-owned that is under 40 feet. (length overall) However, I prefer over 40. And seeking an aft cabin layout.

What is available is twin Lehmans or Perkins from 240 total HP up to Cummins and Cat approaching 800 or more. The lower HP being older boats and the higher being newer. All of that packaged in a 40 to 44 foot length displacing high 20 thousand to mid-30 thousand pounds.

Usage is necessary to consider. Likely to be based in the Gulf or more likely up the Tenn-Tom. With aspirations of coastal cruising. (sorry just not a fan of Fla)

Given that, not sure I understand the bigger HP package. However, I do understand it is not about now. It is about the market when those were built. It seem to me that the market demand in later built boats was for a much higher hp. If one were at some distance from the coast with weather going bad rapidly, any added speed would be desired.

 

[Iggy]

I have a 40 foot full displacement hull and 1700 gives me between 7 and 8 knots depending on conditions. I do it with less then half of your horsepower and zero laboring from the engine. At that rpm I’m burning a bit less than 2gph.

As mentioned, I don't know enough about this topic. I do know that my boat is 26,000 to 28,000 lbs. Maybe yours is lighter? I burn about 4gph.

My engine is a 2001 model. Yours might be newer giving you better results. But the point to this topic, with all things being equal. Is bigger better?

 

[twistedtree]

Back in the early days, a not-so-popular option for a Grand Banks 42 was a single 120hp Ford Lehman. It would easily move the boat at 8.5-9.0 kts. Fast forward 30-years and many were equipped with over 600hp combined and would do 18-20 kts.

I believe that corresponded with their hull change from a displacement hull to a planing hull.

 

[mvweebles]

I believe that corresponded with their hull change from a displacement hull to a planing hull.

I would have thought they made changes when they went to Fiberglass, but thought they were always a semi-displacement/planing hull form.

A quick Google search found this article from Denison Yachts, though no idea if it's accurate. A few interesting quotes:

.....the original Grand Banks 42 Classic design remained unchanged until 1991, when the company retooled and made the hull longer by eight inches and wider by six inches.

Although standard equipment on the Grand Banks 42 was always a single diesel engine, the majority of original buyers opted for twin-engine installations. Ford Lehman’s 120- and 135-horsepower models dominated in the 1970s and 1980s, although other engine options were available on some models. Since its introduction, the 210-horsepower Caterpillar engine has been a popular choice among Grand Banks buyers due to its ability to operate efficiently at displacement speed.....with twin 210 Cats, it cruises at about 10 knots on about 9 gallons of fuel per hour. However, it is capable of a top speed of 15 knots at 23 gallons per hour.​

GB42s are a good case study for our genre of boats. A pair of 200-ish hp engines would seem a good choice.

Peter

 

[twistedtree]

I would have thought they made changes when they went to Fiberglass, but thought they were always a semi-displacement/planing hull form.

A quick Google search found this article from Denison Yachts, though no idea if it's accurate. A few interesting quotes:

.....the original Grand Banks 42 Classic design remained unchanged until 1991, when the company retooled and made the hull longer by eight inches and wider by six inches.

Although standard equipment on the Grand Banks 42 was always a single diesel engine, the majority of original buyers opted for twin-engine installations. Ford Lehman’s 120- and 135-horsepower models dominated in the 1970s and 1980s, although other engine options were available on some models. Since its introduction, the 210-horsepower Caterpillar engine has been a popular choice among Grand Banks buyers due to its ability to operate efficiently at displacement speed.....with twin 210 Cats, it cruises at about 10 knots on about 9 gallons of fuel per hour. However, it is capable of a top speed of 15 knots at 23 gallons per hour.​

GB42s are a good case study for our genre of boats. A pair of 200-ish hp engines would seem a good choice.

Peter

I’m not an expert on their lineage, but think it was in the 2005 timeframe that sparkman and Stephens did a new hull design. Mine was a 2009 and planed at 23 kts with twin 500s. It might have been coincident with the introduction of the Eastbay line because I believe they shared the same hull.

 

[ranger58sb]

Yes total HP.

In the world called perfect, I would build with a single diesel. Maybe two to three hundred hp.

Usage is necessary to consider.

Given that, not sure I understand the bigger HP package. However, I do understand it is not about now. It is about the market when those were built. It seem to me that the market demand in later built boats was for a much higher hp. If one were at some distance from the coast with weather going bad rapidly, any added speed would be desired.

I think I might be inclined to do the single, too...

But then the builders were probably faced with a market assessment that assumes some percentage of buyers might want to go "fast" -- at least sometimes. "Fast" might only mean 15 kts, but it might take a boatload more HP to get there on a semi-heavy semi-displacement boat...

And then they might also decide to standardize on a configuration like that, maybe assuming more buyers than not might be those tending toward that "fast" thing...

And it might be some makers just thought it too much trouble to offer too many configurations with various power.

Especially if they're also assuming a larger market for twin installations than for singles.

Et cetera...

But at least you can drive a "fast" boat slow. (Mostly, sometimes with provisos.)

-Chris

 

[mmullins]

I agree totally with Action’s original post. The boats we commonly know as “trawlers” have almost ceased to exist. Monks, Grand Banks, even Nordic Tugs are putting 2-3 times the horsepower in hulls that were designed to run with significantly less horsepower.
At 37 feet and 135 horsepower, my boat is actually overpowered to run at displacement speeds. At 7 knots, I’m no where near the 70% load recommendation for my engine. And there is a penalty for too much horsepower. Economy. It takes a certain amount of fuel to run 600-800hp even slowly. Trawlers are and have always been a niche market. Let us have our niche. If you want more power, buy a motor yacht designed for it. There are plenty of great boats designed to take advantage of that power. The new range of “swift” or “fast” trawlers are just traditionally designed powerboats - not trawlers. I enjoy chugging along a 7 knots burning a gallon an hour. If I didn’t like it, I would buy a convertible (Hatteras, Post, Viking, etc). I apologize for the rant, but when I consider replacing my 45 year old boat with something more modern, it doesn’t exist. I’ll end this rant with this quote from David Pascoe’s write up on a 40’ Island Gypsy:

“Why someone would choose this mismatched combination of hull and style is a bit beyond me, but there it is. Fitted with a pair lf 3208 Caterpillars rated at 375 HP each for a total of 750 HP, it cannot make use of all that power. More about that in a minute.”
“The performance of this boat was the real sore spot. With 750 HP trying to drive a trawler style hull up on plane, the steering was just plain freaky. She hit up to 17 knots downwind, but would not track straight and the best the autopilot could do was hold it +/- about 25 degrees in near calm water at 2400 RPM. Manual steering wasn't much better; in nearly calm water, the boat wandered all over the place and I had to work the wheel hard. Putting it into even a gentle turn and she'd heel way over . . . . to the outside of the turn, causing the passengers to hang on for dear life. The handling ability was just plain awful, and the small fiberglass rudders didn't help matters any. The rudders are very thick (about 2") and heavily rounded on the edges. Not only do they offer a great deal of resistance, but are hydrodymanically wrong. In higher seas this boat is nearly uncontrolable.”

 

[ksanders]

Here is the challenge guys.

Do not think about a boat from the standpoint of a retired person.

Think in terms of a working age person that wants a larger boat, and is successful enough to buy one.

That person is busy, like almost all successful people. They have limited time to enjoy being on the water.

But... They have money for diesel fuel.

So they buy the boat that offers the comforts and style they want, along with the speed they need.

 

[mmullins]

Here is the challenge guys.

Do not think about a boat from the standpoint of a retired person.

Think in terms of a working age person that wants a larger boat, and is successful enough to buy one.

That person is busy, like almost all successful people. They have limited time to enjoy being on the water.

But... They have money for diesel fuel.

So they buy the boat that offers the comforts and style they want, along with the speed they need.

As I said, there are plenty of good boats to fill this need. Why re-invent the trawler into a boat it wasn't designed to be?

 

[ksanders]

As I said, there are plenty of good boats to fill this need. Why re-invent the trawler into a boat it wasn't designed to be?

They didn't re-invent the trawler.

They took a planing hull boat and simply added larger engines to meet customers needs and sell more boats.

We look at many boats and think "trawler" because they do not look like a go fast boat like a sea ray, but in reality the hulls are planing hull boats equipped with small engines.

Name your boat...

Unless it has a fully rounded chine (edit aft section) like a willard it in fact a planing hull regardless of the engine size.

 

[mmullins]

They didn't re-invent the trawler.

They took a planing hull boat and simply added larger engines to meet customers needs and sell more boats.

We look at many boats and think "trawler" because they do not look like a go fast boat like a sea ray, but in reality the hulls are planing hull boats equipped with small engines.

Name your boat...

Unless it has a fully rounded chine like a willard it in fact a planing hull regardless of the engine size.

I don't know who "they" are but, a semi-displacement hull and a planing hull are 2 completely different beasts. "Unless it has a fully rounded chine like a willard it in fact a planing hull regardless of the engine size" This would indicate that a 40' Grand Banks and a 40' Bertram have the same basic hull design? I'm not a naval architect so I defer again to David Pascoe's review of the overpowered Island Gypsy.

 

[ksanders]

I don't know who "they" are but, a semi-displacement hull and a planing hull are 2 completely different beasts. "Unless it has a fully rounded chine like a willard it in fact a planing hull regardless of the engine size" This would indicate that a 40' Grand Banks and a 40' Bertram have the same basic hull design? I'm not a naval architect so I defer again to David Pascoe's review of the overpowered Island Gypsy.

Semi planing, like semi pregnant is really a marketing term in my opinion.

Either a hull can be driven to climb up on its bow wave or it cannot.

Yes, designers have optimized some planing hulls like my Bayliner for example to ride comfortably at a bit over 2.0X the square root of the water line length, but make no doubt about it, it is a planing hull

Yes some hulls are optimized for much faster speeds but they too are at their root a planing hull boat.

Look at what makes a full displacement hull and compare that side by side with any boat that can be driven up on it's bow wave, and yes you will see that they share similar common traits that differientate them from a full displacement hull.

Are they exactly the same, of course not, but they all share the trait of a wide fairly flat aft section.

Sorry, but just because a boat looks like a "trawler" does not mean it is a displacement hull boat.

 

[mvweebles]

I don't know who "they" are but, a semi-displacement hull and a planing hull are 2 completely different beasts. "Unless it has a fully rounded chine like a willard it in fact a planing hull regardless of the engine size" This would indicate that a 40' Grand Banks and a 40' Bertram have the same basic hull design? I'm not a naval architect so I defer again to David Pascoe's review of the overpowered Island Gypsy.

As a reminder, Grand Banks has never marketed the "Classic" as a trawler, was always called a "Cruiser," as was my Willard. Trawler is marketing term that gained traction after the 1970's OPEC days when folks really started paying attention to fuel prices. I'm with Kevin - GB has a bit of a keel, but outside of that, fairly similar to a standard motoryacht-style hull. It will obviously plane where my boat wouldn't plane with a pair of Pratt & Whitney's bolted to her deck.

I like life at jogging speed. While I would wince at the thought of burning 25+ gal/hr, I could afford it if I wanted. But I have to wonder how many people buy a boat from the glossy pictures a la Passagemaker Magazine, then run at slow-bells after the first fill-up. I suspect that explains the relatively large engines in many boats.

Peter

 

[Bmarler]

As mentioned, I don't know enough about this topic. I do know that my boat is 26,000 to 28,000 lbs. Maybe yours is lighter? I burn about 4gph.

My engine is a 2001 model. Yours might be newer giving you better results. But the point to this topic, with all things being equal. Is bigger better?

No, my boat is older, heavier. I don’t think bigger is better, I think matched performance is better.
In the seventies, when mine was built, 150 horsepower was probably an easy sell.
In 2001? I doubt it. Just a mind set I think.

 

[mmullins]

I never said Grand Banks were displacement hulls. I have been referring to economical, low-power “trawler style” boats that most people associate with the term “trawler.” My complaint remains, if you want a quality motor yacht that goes 18+ knots, you have a plethora of boats to choose from. If you want the equivalent of the 120 hp Marine Trader, GB, Monk etc. of yesteryear, they are nearly non-existent. As for semi-planing being a “marketing term,” I refer to Eric Sorensen’s discussion of different powerboat hull designs in his Guide to Powerboats.