Over-powered trawler style boats

I hope I'm not breaking any rules by starting this thread with the comments on another, but Reubin Trane comments in the thread provoked me to bring this here. How many of our trawler style of boats are over powered, and why?

Originally posted by Reubin Trane

rjtrane said:

We built the original Great Harbour 37s with a pair of Yanmar 39 HP diesels. During initial sea trials, we recorded top speeds of 8 knots plus.

The move to 54 HP motors was primarily a marketing move - to most shoppers, the 39s seemed too small. Of course, they weren't too small - just perceived as too small.

The larger motors do have the benefit of extra power for fighting headwinds and better single engine performance. Disadvantage, as perceived by some, was the larger motors had turbos while the smaller ones did not (IMO, turbos are a good thing if they are engaged/providing boost at cruising RPMs).

In other words, I agree with those who say that very modest HP motors are all that is required for cruising a boat efficiently - around 1 knot below theoretical hull speed (6-7 knots or so). It makes sense to choose a size that will get you to hull speed; any more becomes reserve power for against the wind and/or single engine performance.

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Very good question! Also I like the new avatar pic.

With 300 turbo charged horses, I consider our 35' Mainship "extra", not "over" powered. Normal 8knot cruise we are probably only using a third of her power, while getting almost 3mpg. However, when called on, she can punch through the 15mph current of the Niagara River heading into Lake Erie. Nice to have the extra power when you need it.

The original 10 out of the first 11 Krogen Manatees were fitted with 50 HP Perkins diesels, according to the Manatee database. There are still some around that haven't been re-powered. I spoke to a Broker some years ago that was offering one of the original Perkins powered Manatees. On a sea-trial in calm, Gulf Coast ICW water, he was able to obtain 7.4 knots in slack tide, turning a 22 X 13 wheel. After the first run of Perkins, the venerable Volvo 90 became the power of choice and was only later enhanced by 100 and 110 HP versions of the same engine respectively.

A popular boat publication showed a max of 7.5 knots from the 90 HP Manatee in shallow Biscayne Bay, near Miami turning the same 22 X 13 wheel. Jim Krogen invited them to re-test his own boat in deeper water where he claimed 8.5 knots was a more realistic top speed, but they refused and stuck with their own test results. Among Manatee owners with the Volvo 90, it is well considered that the majority of Manatees can reach this 8.5 mark or more. Some private experiments with larger, steeper pitched, or even 4 blade (vs. 3 blade) props produces complaints of increased suet collection on transoms and inabilities to reach max recommended RPM's, according to the old Krogen website.

Since the late 90's, some boats (including mine) have been re-fitted with mills producing up to 160 HP. but featuring identical peak RPM's and similar power curves. My own 140 Yanmar (turning the same 22 X 13 prop) will push my boat to over 9 knots while digging a huge hole. Other Manatee owners who have tested my boat say that they can feel the extra torque and acceleration, but I can't. It appears that everything that needs to be done on a Manatee can happen with 75 HP, and anything more is a waste.

With few exceptions (Kabota for one), manufacturers keep getting more HP out of the same displacement engines, and usually drop the lower HP series since they are no less expensive to build. Most recently, a flood ruined one of the old 90 HP Volvos and the Insurance company bought him a brand new 160 Volvo for a close bolt-in. Duh!? It seems that the more-gently turbocharged diesels are all but gone.

Photos below include the 50 Perkins, 90 Volvo, my 140 Yanmar, and my own boat's stern wave on the way to 9 knots.

ronlord said:

With 300 turbo charged horses, I consider our 35' Mainship "extra", not "over" powered. Normal 8knot cruise we are probably only using a third of her power, while getting almost 3mpg. However, when called on, she can punch through the 15mph current of the Niagara River heading into Lake Erie. Nice to have the extra power when you need it.

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I feel the same way with the 660 horsepower in our Bayliner 4788

I can cruise slow and get great fuel economy.

When I want to go faster, to outrun bad weather, or to meet a schedule for example, 14 knots is only a push of the throttles away.

Overpowered, nope, just right.

Uh Oh. Should I have said "Over Powered Full Displacement Boats"?

There wouldn't be very many full displacement boats that aren't overpowered. You're right. Extra power sells boats. We are all big strong men that want big strong engines. grunt grunt.

Originally I was worried about being underpowered with my 36hp. Theoretically I'm about 50% overpowered. I rationalize it by saying I like the reserve hp to overcome wind & current. I probably only need 25% reserve to overcome wind and current, but in reality that is all I have available, as the raw water cooled block requires flushing and she starts to get a bit hot with the pedal to the metal. So the other 25% just allows me to delay some required maintenance.

With 240hp combined our 60,000lb nearly full displacement boat is far over powered. Our hull speed is achieved at about 1500 rpm at which these engines are producing a fraction of their 2500rpm 120hp rating.

Without considering the boat owners needs and the way he goes forth only full disp boats can be overpowered. They can only use so much .... 25hp in my case w a 30' Willard. Six hp per ton and more is overpowered for any FD boat. Two hp is minimum and about 4hp is Ideal .. maybe 4.5.

SD boats are all different re the amount of power they require and of course the needs of the owner. Marin w his 250hp GB 36 was close to spot on as he ran his engines at about 50% load and 8 (or so) knots. So for him the boat wasn't overpowered. I think the majority of older GB 36 boats cruise at 7 knots and for all of them the same boat is overpowered.

Most FD trawlers have a similar hull and disp (per volume) so have similar power requirements. Some like TAD's Yellow Cedar are designed for efficiency and require less. Some are beamy, chunky and otherwise not very efficient and those could require 5 or 6 hp per ton while very slippery boats like a narrow double ender would only need 2 to 3. But most FD trawlers need about 4 hp per ton.

The early Albin 25s had a 22hp two cylinder engine and was plenty but as hustler pointed out marketing often demands more power to sell the boats. So that's the reason most trawlers are overpowered. And unless you decommission some cylinders in the engine/s or take out one engine of a twin repowering is about the only answer. And the financial hit from loosing an engine is fairly high. One could always make a single out of a twin only to have the other engine die a year later. Finding used engines could be the low ball answer but a good replacement Lehman engine is frequently more expensive than I think it should be. I see occasional fish boat pull-outs on the cheap on Craig's List. Good engines like an Isuzu come to mind.

What is wrong with extra power? I repowered my 44000 lb boat from 290 hp to 400 hp when I had the chance and haven't regretted a bit of it. I can go slowly and get way better economy than before the change, and I can go a little faster if I need to. With my Semi Displacement hull I can't get to a plane with only 400 hp total ( I think I would need at least 800 to plane) so any extra throttle after 8.5 knots is just digging a bigger hole. If I encounter conditions that require a little extra push, I have it and will use it. The rest of the time, I can enjoy slow, and economical cruising.

I can think of lots of situations when that "over-power" and a little extra speed came in handy, In tidal currents at Dodd Narrows, Deception pass, crossing Straits of Georgia and Juan De Fuca in rough weather to name a few. There are times when fuel consumption and economy are the least of my concern.

It's all a matter of perception . . . With large engines, you always have the option of going slower, but with an undersized power plant you can't ever go any faster.

Extra horsepower does not help a full displacement boat in tidal currents. If your maximum speed is 7 knots at full revs in still water, when you run against a 6 knot current, you will only be able to do 1 knot regardless of your extra horsepower.

The extra reserve in hp does come in handy pushing against the wind, as this is an additional force that needs the extra power to overcome it.

There is a clear distinction between a displacement hull and a "semi-displacement" hull. A pure displacement hull just digs a bigger hole and pulls up a bigger wake with very little additional speed after it gets to a certain point. Any one that talks about going 9 or 10 knots cruise on a 36-40 foot waterline is clearly in the semi-displacement mode and burning way more fuel than I can afford. Not that 15 knots would not be handy at times......

Edelweiss said:

I can think of lots of situations when that "over-power" and a little extra speed came in handy, In tidal currents at Dodd Narrows, Deception pass, crossing Straits of Georgia and Juan De Fuca in rough weather to name a few. There are times when fuel consumption and economy are the least of my concern.

It's all a matter of perception . . . With large engines, you always have the option of going slower, but with an undersized power plant you can't ever go any faster.

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Unless you turn around

she can punch through the 15mph current of the Niagara River heading into Lake Erie. Nice to have the extra power when you need it.

The world dosnt work that way , as noted above .

Many times either the add dept picks the power level or the purchasing folks.

Wonder why there are so many Volvo powered boats?

The engines are frequently priced to be the lowest cost to OEM , who hardly care about maint costs after the boat is sold.

Most all 40-45 ft displacement boats that require smaller engines find the locker almost bare of 75 to 100HP heavy duty engines.
The 75 HP JD Jap marinization is too pricy for most entry level boats.

So they will go for auto rated taxi or farm equipment lighter duty engines that have high peak HP numbers but are useless at those ratings.

Underloading can be a problem but a 120-135 taxi/lorry rated diesel does just fine at 40 (2.5 GPH ) trawler crawling.

Best concept is to find the engines displacement and figure most can make 1 HP for each 3 Cubic inches and survive that loading long term..

FF I totally agree, the more "iron" HP/CID the longer an engine will last (generally). Engines with high HP ratings from small displacement are high strung, running at high intake psi requiring large after-coolers and less tolerant of any abuse or lack of maintenance. Look at any yard doing re-powers and you will find the most replaced low hour diesel is the high HP small (lightweight) powered boats.

Yanmar while a good engine is not a high hour (5000+) engine and requires close attention. When the time comes to pull most are not rebuilt.

I was at a yard 5 months ago and looked in on an engine replacement where both Yanmar 370's were being replaced because of catastrophic failure of one and nearly to the other due to hard use (this boat would run 30's and did quite often). The engines had less then 600 hours on each.

They sure were lightweight for the hp, but aluminum, heat and salt water don't play well together, I was told the cause was after-cooler clogging and corrosion with subsequent overheating and warping with salt water ingestion.

Going fast costs a bunch of cash.

I have a 49' 60,000 lbs. Grand Banks with twin Lehman 454CID 355 HP engines. I would be much happier with twin Cummins 210 HP. I am way over powered. Hatteras built their 58' LRC with 4-71 and 6-71 DD engines. For years the 4-71s were looked down on. Now with Fuel at $ 4.00 a gallon the hull value of the 4-71 powered vessel has come back up. 8.5 knots cruise with the ability to do 10 is perfect for my needs.

The Kady Krogen 42 originally came with the Ford Lehman 120 then in ~1985 changed to the SP135. Later they came with either Perkins, John Deere and a few others but all 130 hp plus.

Fully loaded (44,000lbs) we need a little over 87 hp to reach a hull speed of 8.4 knots. To cruise at 7 knots we are only using ~51 hp. This assumes clean bottom, no wind, no waves, etc. We have 2 alternators and paravanes so the numbers would be a little higher but we are still not using the hp we have. The only time we have come close to using it is when we have towed other vessels and once when we were soft grounded and we able to power off. If we were to repower, I would probably go with ~100-110 hp.

Well, if you are a purist and only accept the definition of a trawler as a round bottom, displacement hull cruiser, then that gives you one answer to the question. But even with that restricted definition of what is a trawler, those boats that meet that definition: Krogens, Willards, Nordhavns, some Selenes are not overpowered.

Specifically the Nordy and Krogen have engines that will easily drive the boat to hull speed and a bit more for wind, waves, etc. They efficiently cruise at about 1/3 of full power and at that power loading the engine will last forever.

But if you open up your definition to include most of the boats owned by members of this forum and those include mostly semi-displacement hulls, then these boats aren't overpowered for their mission either.

When we lived on the west coast we had a 2006 Mainship 34T fly bridge trawler. It looked like a trawler and at low power- about 40 hp, it operated like a trawler at displacement speeds. But that was only about 1/10 of its available hp of 370.

But I could if I wanted to, open it up to 200-250 hp and cruise at 12-13 kts. It wasn't very efficient at that speed, but it did what I wanted it to do.

Was it a trawler and was it overpowered? Only you can decide.

David

Florida Bay Coasters- Key Largo & Florida Bay

When we first introduced the Florida Bay Coasters in 1988 with the 50' "Florida Bay," we chose a pair of Lehman 120s. These were perfectly sized for the 120,000# Coaster, providing a cruising speed of 8 knots (never did reach predicted 10 knots, though).

When building the 65', 160,000#, "Key Largo," we thought a bit of "extra" HP would be a good thing, so we installed CAT 3208 turbos at 320 HP each. We NEVER used the HP provided for by the turbos - in fact, the most expensive repair was to a turbo due to lack of use. When we did put the hammer down, we dug a hole and blew out a LOT of black smoke. We would have been better advised to use the NA 3208 at 210 HP each.

Over the production life of the Coasters, we installed lightweight Yanmars (still working OK after a single owner of over 20 years), 4 cylinder Fords (rough), 6 cylinder NA Perkins 135 HP (smooth and reliable). As long as we had enough HP to counter head winds (the Coasters have an impressive amount of windage), they were never going to exceed their hull speeds.

Not mentioned in this discussion of over-powering is propping correctly. With a FD hull and a wall at the hull speed, if one over powers, then when running at the real cruising speed, not only is the motor running off its peak performance, but so is the prop. To meet the engine manufacturers requirements, the prop is sized to hold back RPMs at WOT. With a prop sized to an overpowered engine, most likely, the prop will not be as efficient as possible at the cruising speed.

With the advent of modern diesels (read: computer controlled, common-rail or similar electronic injection), it does not hurt the motor to run below optimal RPMs and it will retain fuel efficiency throughout its power curve (except at the lowest and highest RPMs).

Being a retired diesel mechanic I didn't want a engine with a turbo. In my experience turbos are great for adding horsepower & fuel efficiency. But along with that comes a lot more maintenance & for a turbo failure to ruin a engine when pieces get into a cylinder. I'am very happy with my EH-700 Hinos with 175 na hp, the best thing any of us can do for our engines is to perform the proper maintenance at the recommended intervals & to use them.



No turbo

>But if you open up your definition to include most of the boats owned by members of this forum and those include mostly semi-displacement hulls, then these boats aren't overpowered for their mission either.<

Once you are into a semi planing or full planing hull , only the deck house style and interior is left of the trawler concept.
Twin engines that cant take a grounding and tiny tankage to keep the weight down and interior cabin volume up.
Looking at many of the SP and FP boats the motor yacht style construction and layout seems better than the imitation trawler knock off.

HULL speed is a fine mental masturbation concept but usually useless to displacement boat owners , unless they want to wake an anchorage or dock.

Sail boats with free power will see hull speed , but for most gaining a K or two at the price of $200% or $300% more fuel is only done for 5 min as an engine check.

Think the SQ Root of the LWL, as cruise speed , and how to operate there more efficiently .

Its NOT with an engine with 400% more power than is required.

healhustler said:

How many of our trawler style of boats are over powered, and why?

Originally posted by Reubin Trane

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Is this a problem? For those thousands of "trawler style boats" out there I think not. Answering a non problem is fun a keeps the internet thriving.

Is there a better way one might ask. Of course, spend big bucks and buy a new Nordhavn, KK, Greenline, Great Harbor or special build like Tad Roberts, Sam Devlin or Steve Dashew designs.

It is usually about the money, darn it.

Or buy a properly designed, powered and built USED displacement cruising yacht - seems to be many out there available at value pricing.

I have to jump in here. My GB has the smallest Ford 6 cyl Lehman marinised. It was made in Dagenham England and somewhere around 337 CI and depending on who says, 90-110 HP. I cruise at 8 to 9 Kts at 1700 RPM and can only push it to 12 WOT. My benefit is if I hold the boat to 8+ kts @ 1600 RPM I get 2.5 or better KPG.

The other Lehmans don't get the fuel economy and even the 250 HP can only go maybe 13+ with a lot more fuel burn.

I have a 5500 mile cruise to verify my fuel mileage too.

Larry M said:

The Kady Krogen 42 originally came with the Ford Lehman 120 then in ~1985 changed to the SP135. Later they came with either Perkins, John Deere and a few others but all 130 hp plus.

Fully loaded (44,000lbs) we need a little over 87 hp to reach a hull speed of 8.4 knots. To cruise at 7 knots we are only using ~51 hp. This assumes clean bottom, no wind, no waves, etc. We have 2 alternators and paravanes so the numbers would be a little higher but we are still not using the hp we have. The only time we have come close to using it is when we have towed other vessels and once when we were soft grounded and we able to power off. If we were to repower, I would probably go with ~100-110 hp.

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Larry I don't think a FD boat needs to reach hull speed. The fastest I've ever gone for more than a few minutes is over 1/2 of a knot under hull speed (6.4 knots) and I've never had a real justifiable need to go faster. I've waited for the tide at Dodd Narrows and run at 2 knots for an hour or two but wouldn't have done anything different that I can think of if I could have run at hull speed (7).

I suspect you would be just as well off w an 80hp JD. That would be 3.6hp per ton (a bit low) but I'll bet it's likely you'd have done nothing different with your boat if you'd had the JD. And w the JD I'll bet you could run it very close to the pin .. unlike the Lehman. So you probably have gone for years running under 80hp 100% of the time. We NEVER run at hull speed so what's the point in powering our boats to do so? We should power our boats for 1/2 a knot less than hull speed at a continuous power rating.

And as for windage when it slows us down the resistance of the boat (w a FD hull) descends much more rapidly than at a linear rate so unused power to drive the hull through the water can be used to drive the boat through the air. And if the wind is great the seas will slow us down anyway. With a 40 knot headwind comes 6 - 7' seas in exposed areas and in such conditions I have always reduced rpm by 300. And I've always made acceptable headway.

The JD 80 may be just a tad small for you considering the drag of your stabilizers. Probably need 10hp for that.

As to the original question of why trawlers are over powered jtrane hit the nail on the head saying "The move to 54 HP motors was primarily a marketing move - to most shoppers, the 39s seemed too small. Of course, they weren't too small - just perceived as too small". The expression "bigger is better" is not reserved for anchors. I have an 03 Camry 4 cyl and can't imagine why anybody would opt for the more powerful 6 cyl model. The amount of power a FD boat can use is fixed so over powering is just stupid for them.

But for the majority of boats here (SD) it's hard to say what's over powered and what is not as the boat will always go faster w more power applied. So if you were a manufacturer over powering netted you 90% of potential buyers w an over powered boat and probably considerably less than 50% of buyers w a boat that was powered with what a good NA would specify not pushed by the marketing crowd. I'm guessing that would be about 175hp for a GB 36. Then there's those that think they can outrun weather and those that like to "get up and go" once and awhile. And hear on TF probably most are offended by the sound of a diesel engine working rather hard and would rather "chug along" at very low power.

So some of the reasons for over powering still exist and if you were to compare the cost of fuel and income of the 70s you'd probably be surprised to find out it's not that different than it is now.

We had a 40' wooden trawler, the "Nellie R," built in Maine by Penbo. She was fitted with a DD 453. Our longest cruise was from Miami to Block Island RI and back - I found her to be most economical at around 6-1/2 knots. I don't recall fuel burn nor top speed (I have the log hidden away somewhere and may dig it out).

This was a wonderful boat! Bargain price when I purchased her in the '70s ($23k vs. $56k for a non-optioned Taiwan Albin 36'). She had mechanical steering (rods and gear boxes) - great Freeman autopilot - hold-over plate freezer and fridge.

Here's a pix of one of her sisters I snapped on the Connecticut River last summer.

Just saw one for sale in Bridgeport CT for $11k (online - not in person).

rjtrane,
Wonderful looking boat. She has the same shippy look that the Willard 36 does. Looks like some of the older boats I've seen from SE Alaska's past. I think I'd like the 3-53.

She's way under one knot below HS at 6.5 knots. But if you had run 6 knots she'd have been even more "economical".

I will point out that just because a boat has a hard chine doesn't make it semi planing. Many steel fishing trawlers and river tugs have hard chines and could never think about planing.

I saw some interesting boats in Scotland a couple of years ago. There are significant changes in regulatory requirements based on length so they build "rule cheaters". Short and FAT. There was one that was almost ready to launch that must have had a length to beam ratio of about 2 to 1. Flat bottom with the whole width of the aft section swooped up like a Chesapeake Bay Deadrise for the props. This was to be used servicing an offshore fishery in the North Sea. (Sorry for the thread drift.)