Engine size when using twins

Marin's post #30 reflects my opinion. Get/have a boat that fits your needs and wants. (I didn't move from sailboats to a motor vessel because I needed to travel faster but wanted a more reliable speed, with less physical effort, and a desire to move from an open cockpit to an enclosed pilothouse. Have been too exposed to ultraviolets already.)

I was going to drop it as I figured I'd stated my position and others have re theirs. But there's more to be said and so little time. Going on a road trip Wed very AM for Edmonton Alberta so my input will be spotty but probably better than all these fast balls.

Peter B. wrote;
"I kinda like the fact that my Lehman 120hp is, by Eric's standards, over -powered,"
Actually that's not so Peter. The 36GB is under powered IMO but it's considerably bigger, wider and heavier than your 34CHB. Also I think the CHB hull is a tad bit more of a FD hull than the GB. So the 120FL seems to be plenty for the 34CHB and because of the over heating problem ect most won't run an FL very hard so in reality you don't really have 120hp. An 80 Cummins or old Perkins should do fine and that's about as much power as you have available. So no your CHB is not over or under powered IMO.


N4712 wrote;
"I too also like the reserve HP for those few times you need it"
Edelweiss wrote;
"We were crossing the straits of Georgia NewCastle Island to Welcome Passage in BC, running with a 42' single engine TT who only made about 6 knots.

Normally I wouldn't care about running slow, but the weather came up and we were getting our behinds kicked wallowing around in the slop with 20 miles of ugly highway ahead of us and three kids who were turning green. We started the second engine, wished the other skipper well, kicked it up to 11 knots and made the crossing in half the time.

Very thankful to have the extra speed on occasions like that!!"

That post brought about some new views of mine on the FD/SD differences.
I remember the "slicer/puncher" bit Mark brought to the forum some time ago. I think Mark knew more about what he was talking about than all of us did including Mark.
For years I've said I never needed more power when it got rough but over and over again many here said they did. I of course decided it was "all in their heads" and couldn't understand it. Cuz I certianly didn't need more power. I always reduce rpm in head seas and seem to make good headway for a 6 knot boat.
I suspect that my Willard is a slicer. I proclaimed it was a "puncher" because I thought her wake at speed wasn't really small. Now I think it is (a slicer (relatively so)) and that may be the reason Willy dosn't need more power in the nasty. Most trawlers have a much more blunt bow than Willy (as in PC) and I feel experience much more deceleration dealing w large head seas. And when the bow goes up the stern goes down and the stern (of a SD hull more like a planing hull) creates more drag than running level. This slows the boat down and most likely enough to require more than cruise power. Look at my pics of Willy's forefoot and perhaps it will appear to be a hull that can slice through waves w little inclination to be impeeded by them.
Edelweiss perhaps if you had a good FD hull you wouldn't have felt the need to go faster. If you had bigger rudders and a stern that didn't tend to yaw the boat around a lot and having kids turning green you may have been fine w buddy boating w the 42.

Marin wrote;
"Absolutely. If the boat won't sell, then it's a bad design. It's that simple."
I can't believe you (one of the smartest guys here) said that.
It's clear that if you were working for a boat builder you'd be better off on the marketing dept than in design and engineering. The latter seems to have escaped you.

Craig wrote;
"No you're just looking for an argument Eric."
No .. and I'm a bit offended by that. I'm just trying to express my opinions so people understand what I'm saying and not to have so many tomatoes fly'in by. Just trying to make my point. That is that speed is fine and mismatched hulls and engines (power) are not.
"Apples and oranges Eric, comparing a Grand Banks and a Willard hull is akin to comparing a Camry to a T-100 pickup."
Most of our boats are better looking than a Toyota PU. There I just compared them. An aircraft Carrier is in some important ways comparable to a row boat. Both FD hulls subject to the dynamics of hydraulic forces of physics to achieve the speed they do. ect ect.

Marin your post #25 is off topic.

Art I'm not telling anybody what boats they should have. I am, however pointing out that some boats are flawed re the powering issues. On The Rocks ... the OP wanted to know.
OTR you're right the smaller engines should be more efficient. Look for very close to 4 to 5 hp per ton of displacement while cruising. Just my opinion though.

Soldier on Mark and thanks for the "slicer/puncher" outlook.

When one is enjoying the attributes on an over-propped, overpowered, full displacement hulled riverboat/trawler much pondering of "good design" occurs. I just spent 5 days underway dawn to dusk in such a boat. I am convinced once again of the positive attributes of over-propped, over-powered, full displacement. The over-propped 100 HP Westerbeke sips 1.5 gal. of diesel while providing a low level of background noise and 7 Knots at 1,600 RPM. I consider this level of performance GOOD! I could probably make 7 Knots with a Perkins 4-108 geared and propped to turn 2,800 RPM burning 1.5 Gal per Hour. But the last thing I want to do is live with a 4-108 turning 2,800 RPM all day.......And when the bridge ahead will be opening on a schedule I can push the throttle up to make 2,000 RPM and 8 knots and make the 11:00AM opening. Try THAT with the 4-108! Admittedly the Westerbeke specifications for WOT RPM cannot be met by my boat. And the negative effects have yet to be experienced as my engine is running at perfect temp, oil pressure, and without smoke. But as a benchmark a sistership has the same motor and propeller and is running strong at 10,000 hours. If my engine reaches this 10,000 mark I will either be dead or it will belong to someone else. And if my motor dies at 7,500 Hours because of over-propping that will be OK too. Because if I had to listen to a 35HP engine power my boat for even 1,000 hours I would have tied my Rocna anchor to my neck with chain and jumped overboard........

Billyfeet,
In this case a CQR would work just as well.

When looking for a boat, the choice was either slow, 7+/- knots (my boat now) or fast, 15+ knots. The thought that plowing along burning lots of fuel at 8 or 9 knots as opposed to 7 knots is just lost on me. As with Art's Tollycraft, if you want to go faster and pay for the extra fuel, then should be able to cut half or more of the time to your destination. Just don't get doubling or more the fuel burn to add a knot or 2.

Ted

Why not have it all? The ability to economically cruise along at hull speed combined with the ability to kick it up to 10, 12 or egads even 16 knots when desired seems a very popular choice. Lots to choose from in this regard. If one is seeking the lowest possible fuel burn in a displacement pleasure vessel, well laid out sail boats are easy enough to find.

I'n headed to the Seattle Boat Show, wonder how many full displacement motor vessels will be there, other than very expensive Selenes or Nordhavns? Therin lies the rub, full displacement "new" is big bucks, which is not necessarily an overall cost effective way to travel. There is much more to economic boating than a low fuel burn per hour, much more.

sunchaser said:

Therin lies the rub, full displacement "new" is big bucks, which is not necessarily an overall cost effective way to travel. There is much more to economic boating than a low fuel burn per hour, much more.

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The cost of fuel is such a small part of the overall cost of owning a boat. I can't help but wonder why the average pleasure boater would be overly concerned about the expense. The difference between 3 gallons per hour vrs 5 gallons per hour is insignificant given the distances we travel. Unless you're a world traveler and constantly on the move. IMHO, the actual savings would be insignificant for me.

Reminds me of a friend years ago, who only bought cars with stick transmissions. At stop lights he turned the engine off, on hills he put the car in neutral rolling down the grade, and on longer down grade he also switched the ignition off all to save a little gas.

Some of us easily travel 400 to 500 hrs per year.

The difference between 3 and 5 gph would be the difference of 1200 versus 2000 gal per year.

At $2 a gallon not so bad but when a lot of places it was over $4 a gallon ....that could easily be between $3000 to $4000 per year.

For many here that may not be a spit in the wind to their bank accounts...to others it's a new RIB or a genset or upgraded solar...etc...etc...

As many TF discussions...totally different audiences sometimes.

O C Diver said:

When looking for a boat, the choice was either slow, 7+/- knots (my boat now) or fast, 15+ knots. The thought that plowing along burning lots of fuel at 8 or 9 knots as opposed to 7 knots is just lost on me. As with Art's Tollycraft, if you want to go faster and pay for the extra fuel, then should be able to cut half or more of the time to your destination. Just don't get doubling or more the fuel burn to add a knot or 2.

Ted

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Hi Ted

Regarding our Tollycraft... a delightfully classic boat... in relation to what you mention, we basically have two cruise speeds.

1. 16 to 17 knots on full plane to get some place quick. That really works well when you have 130 +/- miles to cover on a short schedule for the day. At that speed my baby twins together consume 1 gal per nm (16/17 gal per hr. total). Hurrying along at that speed can cost some dinero; especially when prices are high! Our Tolly tri cabin is designed so at that speed people can hang-out in salon and chat in normal voice levels. On the flying bridge all you hear is the rush of water alongside her hull and the sweet resonance of exhaust with motors synced to rpm harmony. Oh yea, you also hear the occasional squawks of seagulls and get to watch seals and other sea life.

2. 6 to 7 knots which is bellow calced hull speed of 7.58 knots. With both engines loping along the motor sound is minimal, synced rpm harmony provides a really nice beat to enjoy, and she gets right at 2 nmpg. Not super-duper mileage… but acceptable (to us) considering other features and creature comforts our Tolly provides.

We also sometimes cruise on only one motor at 5 to 5.5 knots and get 2.75 +/- nmpg

Then there is always the “Big Blast” available of pushing both engines to over 4K rpm and speeding along at 21 to 22 knots. I’ve only needed to briefly utilize this WOT power/speed three times. Once on sea trial for timed minutes to make sure engines worked well and could take the gaff… if needed. Once for less than two minutes to escape away from a confeck-uration of idiot boaters gathered around the “The Maltese Falcon” entering SF Bay in 2009. And, once for way less than a minute during a close call with several boats where it was wise for me to substantively change course and position. Don’t ask what gallons per hour at that level of speed… cause I don’t need ta know and I don’t need ta care… just glad it’s there when needed or desired!

All and all, I pretty much baby every portion of our Tolly. She’s a gasser, but, she’s a good gasser – and – Comfortable/Fun as Hell! I believe with correct maintenance and thoughtful use she’s got many years of enjoyable service remaining.

Happy Boating Daze! - Art

Pict (by friends passing by) is me and grandson Cooper with buffer in his hand... 11/1/14.

IMO the cost to the maker of somewhat larger engines is a small part of the cost of construction. For the reasons stated above they would not want to try to sell boats that could be considered under powered. More power appeals to most people. Fuel prices up to 1998 or so were less than $1 per gallon and people buying boats back then didn't have a political point to prove.

From what I remember Willard took sail boat hulls they were selling and converted them to power in an attempt to expand their market.

Coot: have you ever faced strong head seas with wave after wave stopping the boat with that set up?

Every time head seas presented a problem with my boat...I had to throttle back not up to make the ride bearable...

The ONLY time I have throttled up in this boat (and usually only 200 rpm or so) was in flat water to overcome a 3 plus knot current or pass some one where passing time was critical.

If/when I repower, I would have no issue with dropping to 80 to 90hp.

But that is me and I'll have to think long and hard if that may affect resale...if I care at that point

For those who worry about fuel burn and speed I direct you to the Jan . issue of Wooden boat Magazine and an article about LDL boats. The article Motor Boats Of The Future pg 52 featuring work by Nigel Irons. What you get in an LDL boat is long skinny and low and light with the ability as a SD to go well beyond the old estimate of waterline related hull speed. So with small or modest HP one can get good sea keeping ability with great mileage and speed.

And pay more for dockage, hauling, space issues...etc..etc.....

Plus the are few out there and no where the price of what many can afford....

There may be a few... but not many....

Low resistance boats have been around a long time..nothing new....just new marketing.

Buying what you want and running it economically is what most do...saying fuel or any other particular boating cost is a particular percentage is conditional...not universal.

If I were a wise person, I'd probably not add a comment to this thread, but my rationale is different from many here while resembling many.

My Tiara is a deep V, full planning hull that will do 31kts at wot and burn 46gph while doing so. She also haas a 14'6" beam and very stable (especially for a deep V). Is this a long range cruiser? When I throttle back to 8.6 kts (hull speed) I am burning 4.7gph combined using both engines. Our range at hull speed is 838 miles (maintaining 20% reserve). With the build quality of this boat and how she is equipped, I would not hesitate to cruise anywhere within her range, including through the Panama canal, or even further, thus making her an excellent (for us) cruising boat.

For those whose SD hulls allow 16 or so kts, you understand the "need for speed" when get home in bad weather matters. Since we are retired time is not critical for trips. What is critical is my viability and the number of years I have left to cruise comfortably. I am in my 70's and a recent cancer survivor. That is a wake up call for more speed.

Many times our purchase and life decisions are based on perceived value. This value may be different for many people, hence the proliferation of so many designs.

psneeld said:

And pay more for dockage, hauling, space issues...etc..etc.....

Plus the are few out there and no where the price of what many can afford....

There may be a few... but not many....

Low resistance boats have been around a long time..nothing new....just new marketing.

Buying what you want and running it economically is what most do...saying fuel or any other particular boating cost is a particular percentage is conditional...not universal.

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The thing I see about LDL boats is that they lend themselves to home build with stich and glue composite build. Since they are simple and light with small motors not so expensive to build or run. Yes the added length will cost more at a dock but many do a lot of cruising on the hook and the fuel savings would possibly balance out the other added costs of length. What the LDL can not do is make a good cottage on the water. On an LDL you and the admiral will know you are on a boat.

Both of my favorite boats are SD so I haven't got my head in the sand and I'll admit I went overboard a bit looking for a 1gph boat. I realize now (especially now) that 2gph would be really fine.
Earlier I criticized the GB and got some pissed at me (especially Marin) by calling it a "bad design". I should have chosen other words like flawed design or a power platform that's not ideal. At any rate if the flaw was very significant I would not consider buying them and I could easily buy a 36 or 32 if moorage fees were not so high.
And I'm not sure how much the efficiency of the Willard drew me to buy one but even more important is that I think the W30 is just a really good designed boat. Do I like the plastic windows ..NO .. Do I like the steel in concrete ballast .. NO. and there are other features I'm not fond of.
Can't say I've changed my mind about the power in the GB or others like it but as a flaw it's not a big one and I appologize to any GB owners that were offended by my bad words.

manyboats said:

Both of my favorite boats are SD so I haven't got my head in the sand and I'll admit I went overboard a bit looking for a 1gph boat. I realize now (especially now) that 2gph would be really fine.
Earlier I criticized the GB and got some pissed at me (especially Marin) by calling it a "bad design". I should have chosen other words like flawed design or a power platform that's not ideal. At any rate if the flaw was very significant I would not consider buying them and I could easily buy a 36 or 32 if moorage fees were not so high.
And I'm not sure how much the efficiency of the Willard drew me to buy one but even more important is that I think the W30 is just a really good designed boat. Do I like the plastic windows ..NO .. Do I like the steel in concrete ballast .. NO. and there are other features I'm not fond of.
Can't say I've changed my mind about the power in the GB or others like it but as a flaw it's not a big one and I appologize to any GB owners that were offended by my bad words.

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Heck Eric

I wouldn't say you had bad words... just boat-luven words regarding your preferred type/design boat. We all have high praise toward our preferred boats. That's one of the many things that makes boat-luven so much fun!

Happy Boat-Luv Daze - Art

PS: How boring mariner pleasure-boat life would be if we all liked the exact same type boat!

bayview said:

Coot: have you ever faced strong head seas with wave after wave stopping the boat with that set up?

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Hardly noticed a speed drop; the Coot just "bullies" its way into seas, perhaps because of its heavy displacement (14 tons). If seas are heavy, I lower the throttle to reduce the quantity of spray and the boat's motion.

Ziggy8321 said:

If I were a wise person, I'd probably not add a comment to this thread, but my rationale is different from many here while resembling many.......
Many times our purchase and life decisions are based on perceived value. This value may be different for many people, hence the proliferation of so many designs.

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And opinions!! Good post and I totally understand and agree with the getting older issues!!

P.S. Never be concerned about stating your opinion on this forum. After all it's what you believe and if somebody doesn't agree. Tough tomatoes, they'll just have to get over it!!

manyboats said:

Marin wrote;
"Absolutely. If the boat won't sell, then it's a bad design. It's that simple."
I can't believe you (one of the smartest guys here) said that.
.

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That's why I'm one of the smartest guys here.

Our (Boeing) design engineers have come up with some really cool and extremely good designs over the years that have never seen the light of day. Why? Because the airlines or the military didn't want them. To them, they were bad designs. Why? Because they didn't do what they wanted to do.

You have two major flaws in your beliefs and position. One, you assume the only good design is what YOU want, which is a glacially-slow displacement boat with very low power. You do not represent the vast majority of the power boating market. In fact, I would say you represent a very tiny fraction of the power boating market. That is easily proven by looking at what sells and what doesn't. How many Willards and Coots have been sold vs. how many Bayliners, Grand Banks, Californians, CHBs, Flemings, Sabres, Eastbays, and the list goes on.

Two, you assume that a theoretically good design is all that is needed to make a good product. You repeatedly claim that a Grand Banks, for example, is a bad boat because they didn't use the design theory you adhere to of very low power and a displacement hull. This is way, way wrong. A truly good design is one that combines the theories of what make a good, efficient design with the practicalities and realities of what make a desirable, producible design.

By focusing only on the theoretical and not the practical, your arguments have no meaning or application in the real world. Which is why most production boat builders would totally ignore your definition of good design if they were exposed to them.

I know you like theory over reality, but that makes for a very lonely position. We've had some excellent engineers here over the years who insisted on following theory and said the customers would simply have to accept what we produced. We know best, they said, because we have aerodynamic or structural or whatever theory on our side. These engineers, as smart as they were, didn't last long at this company because they refused or were incapable of understanding that customer requirements and desires and producibility trump pure theory every time. These engineers were incapable of adapting their theoretically perfect designs to the reality of producing a product the market wants.

The same is true of production boat building. If a designer or engineer cannot accept that the number one objective is to produce a boat design that the customers want and is producible to a certain cost point, but insists instead on giving priority to the theories of hull design, power to weight, etc. regardless of customer desires and production cost, that engineer will not have a very long career at that company.

You say you're surprised a "smart" person would not accept your ideas about design theory. In a career first in television producting commercials to sell products and services to a market, and then in aerospace helping to sell incredibly expensive products to a market comrpised of extremely picky customers, I can say with extreme confidence that focusing on design theory alone is not a smart approach to success. Focusing on customer requirements, production cost, serviceability and design theory is a smart approach.

And if you do that, the end product will be a very good, very smart, very successful design.

PS- My post #25 was a direct response and reinforcement to what Peter said in his post #18.

Edelweiss said:

...Reminds me of a friend years ago, who only bought cars with stick transmissions. At stop lights he turned the engine off...

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Your friend`s actions are reproduced in numerous cars fitted with "stop/start" technology.

BruceK said:

Your friend`s actions are reproduced in numerous cars fitted with "stop/start" technology.

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Very true with modern vehicles, but dangerous and illegal with 1965 technology. You lost your power steering and brakes when you turned your engine off!!

Greetings,
Mr. mb. "...I can't believe you (one of the smartest guys here) said that..." One of the other smartest guys here agrees with Mr. Marin. Moi.

Art said:

Heck Eric

I wouldn't say you had bad words... just boat-luven words regarding your preferred type/design boat. We all have high praise toward our preferred boats. That's one of the many things that makes boat-luven so much fun!

Happy Boat-Luv Daze - Art

PS: How boring mariner pleasure-boat life would be if we all liked the exact same type boat!

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I guess I have a boat love problem. I like, not love, many boats of diverging types oar-paddle-sail-OB-Inboard-SD-FD-one or two motors-wood-steel-FG-Al- and composite. Since I don't love em I tend to see the good the bad and everything in-between. I can defend or diss most boats after all are they not all a bundle of compromise.

manyboats said:

Marin you're notion that everybody wants to plow along as fast as you is more correct than wrong but misses the mark by a mile thinking everyone's like you. But the market shows you're more right than wrong.

.

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The market shows he's far more right than wrong and that's really where you miss the point, that you're in the huge minority. Most power boaters do not want to run 7 knots for many reasons and it has nothing to do with cars, it has simply to do with preference of speed on the water. You post the theoretical hp required, very informative from a technical and engineering aspect, but people don't buy based on technical data and an engineer's perspective. I've asked the question of engineers many times when they had an improvement on a product that only cost a small amount, "How are you going to market this added value?"

Personally the slowest boat we've ever owned cruises at 20 knots and WOT is 25 knots. Now we also understand on a trawler forum we're even further out of the mainstream than you are. But that's fine. We have our preferences and don't try to push them onto others. Frankly, we felt we were slowing down greatly as our last boat when we lived on the lake ran around 55 knots. Now we do occasionally run 15 knots, even 12 knots. Especially 12 at night. But 7 knots has never crossed our mind.

And I'm sure you'd have even greater issue with our ribs.

eyschulman said:

I guess I have a boat love problem. I like, not love, many boats of diverging types oar-paddle-sail-OB-Inboard-SD-FD-one or two motors-wood-steel-FG-Al- and composite. Since I don't love em I tend to see the good the bad and everything in-between. I can defend or diss most boats after all are they not all a bundle of compromise.

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We do equally, love them all. Doesn't mean we'd love to own them all, however. We have our personal preferences.

Manyboats.....

First we think your boat is very very cute and unique and love it from that aspect. However, where is Willard now? The demand for such a boat just wasn't broad enough. That makes your boat even more special as not one everybody is rushing out to buy the new one of. With GB, it's just another GB. But not with Willard, it's unique and special. Built for the person who wanted to go a different route.

Most cruisers, tugboats, and ships in my home waters travel at speeds of 8 to 12 knots. Faster boats are typically recreational fishermen, ferries, Coast Guard, Sheriff, and Highway Patrol and just plain speed boats.





We enjoy life in the slow lane (six+ knots) along with the real (with net) trawlers, commercial fishermen, and sailboaters motoring.