Electric Boat Engines

I was talking to a customer the other day and he was telling me about this 70 footer out west that uses a 14KW generator with twin electric turbines to cruise at 25+ knots, no kidding.* Seems they have*taken the locomotive concept and made it work for a boat.* A single generator, I am told, converts AC to DC which powers the DC engine.**No storage batteries are used.

Has anyone heard or seen any of this?* Sure looks promising for repowering to me.* I can think of tons of things to do with the* space 500 gallons of fuel uses up

MT

There was a fairly extensive discussion of this on the Grand Banks owners forum not long ago. To the point where people were naming specific products that could be used. The general consensus was that, while the theory is good, it suffers from a problem of scale. Many if not all of the early Washington State ferries were diesel-electric and they worked great. The last ones have just been removed from service because after fifty-plus years of service their hulls are too corroded to repair economically.

But it seems that as a propulsion system for smaller boats like our trawlers, the savings are not really there. If I'm remembering the discussion properly, there is quite a drop in power output from the prime mover (diesel) to the generator to the motor. So in order to get sufficient current to operate an electric motor powerful enough to run a trawler with the same speeds we have now, you'd need a prime mover just about as large as the diesels we use to power the boats directly with today. And you'd have four components--- the prime mover, the generator, and the motor/gearbox to stuff in the engine room instead of just the two, the prime mover and the gearbox, that we have now.

The reason diesel-electric was used for the ferries (and is for railroad locomotives) has to do with control issues, not economy issues except for the fact that electric propulsion is a LOT more efficient than steam, which is what it replaced in the ferries and locomotives.*

A purely electric locomotive-- one that gets its power from a wire-- is much more efficient than a diesel-electric locomotive if you just look at the locomotives. However, when you factor in the support system needed for the pure-electric---- maintaining the trolley system, generating the power, and so on--- the diesel-electric was less labor intensive and so was considered more efficient. Given the price of fuel and the potential for other means of generating electricity-- nuclear, etc--- pure electric is far more efficient, and is why in Europe the diesel electric locomotive is fast becoming a thing of the past.

That's not to say it won't work in a smaller boat, but there does not seem to be any real advantage to it. And apparently there isn't any advantage in large ships today. The two attached photos are of the most powerful diesels made in the world today, designed for container ship use. The crankshaft is for a 10-cylinder version, the complete engine is a 12-cylinder version. The 14-cylinder version burns 1,600 gallons of fuel an hour.* If diesel-electric was more efficient, they wouldn't be doing this.

-- Edited by Marin at 17:00, 2007-12-27

Could someone please tell me what an electric turbine is????

MT,

Sounds like fairy tales but such Propulsion for yachts exists. I thought it was in PMM but my
cross reference guide has failed to locate the issue. I will keep looking and get back

Eric Henning
30 Willard
Thorne Bay AK

Diesel-electric systems have been used on large vessels -- cruise ships, tugs, naval vessels, ferries, etc. -- for years. But, as Marin said, the systems were too large, too heavy, and too expensive to be practical for small boats.......until very recently.* All of the components have gotten much smaller, lighter, and more effiecient.* Some of the new electric drive motors claim a 98.9% efficiency rating.

Fischer Panda has a system up and working. They used a 35 foot motor sail boat as their test boat.
http://www.solarnavigator.net/fischer_panda_diesel_electric.htm
Be sure and check the links at the bottom of the page.

Ossa (from California) has a system ready.
http://www.ossapowerlite.com/overview.htm
They have installed in as small as a Legacy Yachts 32' MKIII. Be sure and read the FAQ and the tech library pages.

Nordhavn is going into diesel-electric. Their new 72 footer will be built with this technology.
http://www.nordhavn.com/constr_con/diesel_electric.php4
"Like its larger commercial cousins, the hybrid 72 uses its diesel engines exclusively to drive electric generators; there is no direct mechanical connection between the engines and propellers. The electricity produced is then used to power electric motors that drive the yachts propellers." This is a quote from the above link.

Diesel-electric is coming on strong. And (according to the Ossa FAQ) it takes less electric HP to produce the same results as a gasoline or diesel engine driven boat.* This is supposed to be explained in the tech library page but it's over my head.* I'll leave it to some of you techie/engineering types to say if their explaination makes sense or not.

These are only three results from a quick google search. There are many more for those that would like to investigate further.


-- Edited by gns at 23:44, 2007-12-27

-- Edited by gns at 23:51, 2007-12-27

-- Edited by gns at 23:55, 2007-12-27

Sorry about all the edits to my post. I couldn't figure out why my links weren't working properly.

We had a long discussion on this over on PMM a time ago...

The reason it works with less HP is because of high torque which is available from a dead stop thru full RPM. That means full torque is delivered the moment the prop starts to turn allowing a larger prop with larger pitch, which would normally stall a combustion engine before it could ever get up to the power band.

As an example of low HP w/ High Torque: My 85ft 90ton boat was originally powered with 16hp steam power (steam engines have similar torque pattern as electric). This 16hp high torque steam engine drove the boat to 12 knots and could break 15inches of blue ice with a full head of steam.

That 20hp electric motor could probably drive my boat nicely.

The issue as I understand it is not that there aren't electric motors capable of driving the typical trawler-type boat at the speeds we're used to today. The issue that apparently tends to be somewhat overlooked is that the electricity to run a motor of this power has to come from somewhere, and that somewhere isn't going to be batteries unless you are willing to fill the boat with them and take real short cruises or have a really long extension cord.

It's the generation of the electricity that has so far made this kind of propulsion impractical in smaller boats. The electric motors may be 98 percent efficient or whatever but the prime mover needed to generate the required amount of power isn't. And if you need almost as large a prime mover to generate the power as you need to move the boat directly, why add the additional components and expense of the electric drive?

That's the argument. Now a very easily-moved hull, something like what FF has in his ex-Navy launch or some other long, light, narrow configuration can probably get away with a much smaller motor to achieve hull speed than is needed to move the typical Grand Banks-type hull. And the smaller you can keep the electric motor, the smaller the prime mover needs to be.

But...... if you have a long, narrow hull that can be powered to hull speed with a small electric motor, it can probably be powered to hull speed with a really tiny diesel, too.

Now maybe a very easily driven hull can get by with a motor so small it can be powered by a large battery bank that can be charged from a solar array or a wind generator or a really tiny engine. Then the efficiency advantages may become reality.

But I don't think it's going to be as simple as out with the two Ford Lehman 120s and in with the prime mover- generator- motor/gearbox rig. I think if there is a future for electric motor drive it's going to require a combination of hull design and tailored powertrain design to make it worthwhile.* And the chances are these kind of boats are going to be slow.* 6-8 knots maybe unless the hulls are so long that the hull speed is faster.* The current business of plowing along at 16 knots in a big, heavy boat isn't going to happen with diesel-electric drive unless the prime mover is huge, in which case you're right back where you are today with direct diesel drive.




-- Edited by Marin at 02:12, 2007-12-28

IF we ever get batteries that have 10x + the power density of wet cells , and can be rapidly recharged electric for propulsion may be a go in sizes bigger than a kayak.

For the forseeable future the properly selected,highly loaded diesel will remain thje only choice for trawlers.

The Big Nordy concept of a just barely big enough main engine with a heavy weather boost from the noisemaker is interesting , but thats about all.


Electric will remain the joy of folks with huge and changing hotel loads , and a desire to self dock with pods instead of tugboats.

FF

Hey guys I found it. There is no electric turbine and no electric boat engines but there is diesel
electric propulsion for yachts. After calling engine boats motor boats almost forever we finally have a real motor boat. Maybe we should stop bashing PMM and start reading. The information is in PMM issue june 2003. The diesel electric system used on the example boat was developed for DE propulsion in busses. The two electric motors that drive the boat develop maximum torque at ten
rpm. In a fixed pitch propeller installation the propeller is only matched to the engine ( load wise )
at WOT. In any boat where the propeller and gears are chosen properly that is only at one speed...WOT. At cruising speeds the engine operates at a mutch higher speed than ideal. Some trawlers were over-proped tho compensate for this problem...like my Willard. ( I now have it proped correctly ). For this reason the DE system is more efficent ... 22% in the example given.
Some of the advantages of DE propulshion are:
1 Slow speed operation. One can be continuiosly unded way at any attainable speed... sutch as 1 knot or slow enough to count the revolutions.
2 Manouverability. Made better be very high toqure, no gears and associated problems and more control of propeller speed.
3 Installation lattitude. Engine can be installed almost anywhere and greater lattitude for propeller location is also possible.
4 Less weight
5 Less noise and vibration. Aqua Drive, Python drive and similar drives are not needed.

Information:

PMM June 2003
info@feys.org
FAST Electric Yacht Systems Inc.
10777 Westhiemer rd. suite 925
Houston, Tx 77042

Eric Henning
30 Willard
Thorne Bay AK

The electric motor turns at TEN rpm? That doesn't seem like a correct figure to me........ Are you sure they aren't saying the electric motor is GEARED DOWN to ten rpm?

Marin,

I spelled it out as did not belive you would belive me. The boat in the article has a gear up gear box, in this case 1 to 1.5. So the eninge turns 1000 rpm and the alternator turns 1500 rpm and
the drive motors drive through a 4 to 1 gear to the propellers. The engine/alternator turn at a speed selected by the computer to drive the propellers at an ideal engine speed. Thats why the system is more efficent.

Eric Henning
30 Willard
Thorne Bay AK

One big advantage of electric motor drive is that all the power and torque are available almost instantly. Back in 1918-1919 General Electric built five electric locomotives for the Milwaukee Railroad to use on their 200-mile electrified division through the Coast Range in Washington State. They were known as Bi-polars because unlike other electric locomotives with electric motors geared to the axles, the armatures of the Bi-polar's 12 drive motors were the axles themselves.

Each locomotive was 76 feet long, rode on 28 wheels, and weighed 521,200 pounds. In 1941 a Bi-polar engineer was talking about how fast his locomotive could go and a couple of young enginemen including a fellow named King Clover said they didn't believe him. The engineer told them if they stood next to the front of the locomotive (which was not coupled to a train) he would start it forward and by the time the rear of the locomotive reached them it would be going too fast for them to jump on. Clover took him up on the bet and while they tried several times, no one was able to get aboard the locomotive as the back end went by them. The reason it worked was that the 3,000 vdc the motors used was available instantly from the overhead trolley wire.

I looked through the discussion pages you linked, Eric, and while most of the discussion was way over my head it seemed obvious that while electric drive certainly can work in boats like ours, the power-generation challenge is going to keep it from being practical and affordable for a quite awhile.

PS-- I've found that if you add an extra space after you type or insert a URL it will usually highlight properly.

Don't forget this one, looks good.

a diesel hybrid

-- Edited by JB at 23:12, 2007-12-28

First things first. There are three distinct types of "electric" propulsion systems and they should not be confused.


ELECTRIC SYSTEM: This is batteries powered propulsion only and, as pointed out by several posts, is not feasible for the type of boat discussed here. The only practical use for this system in my opinion is an electric trolling motor on a bass boat working a line of structure in a lake somewhere.


HYBRID SYSTEM: This is a combination of generator and battery bank operation. This is NOT diesel-electric and was not the topic of discussion.


DIESEL-ELECTRIC: This is operation by a DIESEL generator wired to ELECTRIC motors which drive the boat. NO BATTERIES are needed for propulsion, though a house bank would probably, but not necessarily, be included.

Nordhavn is not using "a just barely big enough main engine with a heavy weather boost from the noisemaker". Actually reading the info on the Nordhavn link shows that the diesel-electric unit will be a 200HP Lugger coupled with a 149kW generator that will push this BIG boat to 7.5 kts. and will be the primary engine, not a "boost". Adding in a 400HP Series 60 Cat coupled with a 287kW generator will push the boat above 7.5 kts. (to 9.5 kts.) when extra speed is needed or desired. Using JUST the 200HP Lugger diesel-electric system will give this 73 LOA, 240,000 pound boat an estimated range of 8200 miles on 4000 gallons of fuel at 7 kts.

Marin said:

"It's the generation of the electricity that has so far made this kind of propulsion impractical in smaller boats." and "But I don't think it's going to be as simple as out with the two Ford Lehman 120s and in with the prime mover- generator- motor/gearbox rig."

The FAQ on the Ossa link I gave answers both of these concerns.

"Ten years ago a typical variable-speed industrial motor might have been 85% efficient. OSSA Powerlite motors now achieve efficiency as high as 98.9%. Only two years ago, the lightest 200kw generator you could get weighed over 4,000 lbs. The OSSA Powerlite 200kw generator comes in around 1,400 lbs wet. Add to this is the fact that power electronic devices have declined in cost by as much as 90% over the past ten years and attained a level of reliability that often exceeds that of their mechanical counterparts. Taken together, it means that the time for yacht-compatible diesel-electric propulsion systems has finally arrived."

"Let's say that you would normally use two 150 hp Yanmar engines and a 16kw Fischer-Panda generator. If you replaced this with a single 150kw OSSA Powerlite generator and a couple of 100hp OSSA Powerlite motors you would have a lighter system, better fuel economy and about the same "usable" power at virtually no additional cost. If you instead decided to use two 100kw OSSA Powerlite generators and a couple of 150kw motors, you would get even better fuel efficiency and greater redundancy, and considerably more propulsion power but the cost would be higher."

The two paragraphs quoted above came from the Ossa FAQ. I dont know but I would guess that a 150HP Yanmar weighs in at around 1000 pounds. I think a 120 Lehman is around 1200 pounds. Taking a couple of those out and replacing them with a diesel generator that weighs half as much would give you an <u>immediate</u> boost in fuel economy and probably performance as well since youd be pushing less weight thru the water.

And you wouldnt have a transmission or gearbox in the conventional sense so you would be saving weight and space there as well. You reverse an electric motor by reversing its leads. This is done electronically by the systems controller, not a transmission. The system controller also manages the electric power sent to the drive motor so that the prop is completely de-coupled from the diesel engine of the generator. The prop speed can be adjusted infinitely from 0 RPM to maximum RPM independent of the engine, which, if its a variable speed generator and engine, can continue to operate at optimum RPM for the load it is under.

"In general, one improves propeller efficiency by (a) increasing the diameter and, (b) turning the propeller more slowly." Another quote from the Ossa web site. And with diesel-electric you can do exactly this because the prop speed in independent of any engine.

The last quote from the Ossa web site, this one from their tech library:

"The examples presented and conditions analyzed have shown:

1. A 10% fuel savings achieved by allowing the engine speed to fluctuate along with the load thereby eliminating inefficiencies associated with intermittent high-speed, low-load operation.
2. A 7% fuel savings achieved by using a larger and more efficient propeller than would be possible with conventional diesel drive.
3. A 13% savings achieved by more closely aligning the power required by the propeller and the power produced by the engine and, by doing so, shifting the engine load to a more optimum point on its power curve over a wide range of speeds and conditions.
4. An additional savings of 20% achieved under some load conditions if multiple generator are installed.

The demonstrated fuel savings total 30% to 50% - substantially more than the losses introduced by a reasonably efficient diesel-electric system. Understanding the basis on which these fuel efficiencies are obtained makes it apparent that the efficiency gained over a conventionally powered vessel will vary according to environmental conditions and vessel use and could be more or less than what has been shown here."

I dont have any affiliation with Ossa or any of the companies I linked to. I didnt know much of anything about diesel-electric before I looked at their web sites. But (and heres the rubI am not trying to diss anyone even though I know it may sound like I am. Im hoping this will be taken as constructive comments) I dont think some of the comments made here would have been made if the links I posted had been even quickly scanned. If you (in the general sense) read the info provided and disagree with it, and say that you disagree with it for this or that reason, thats fine. That means a healthy, helpful conversation is going on. But to just repeat unsubstantiated opinion and ignore data from reputable sources serves no one and kills off a conversation and limits educational opportunities.





-- Edited by gns at 23:13, 2007-12-28

Gary,

Thank you so very much for your contribution. I enjoy talking about this sort of thing. It
makes me feel like a pioneer or that I was there at Kitty Hawk. I once felt strongly that way
when I was an early pioneer in ultralight aviation.

Marin,

Where's the problem? Numerous systems seem to be generating the power handly. They are brobably very dependent on the computer/control part of the system that is probably very expensive. I probably won't be able to afford one of these systems but it is fun to learn about
and contemplate them. Rather like the mega yachts in PMM. I like to read about exciting things
and there are many more exciting trawlers than my old Willard.

Eric Henning
30 Willard
Thorne Bay AK

The company I work for recently flew an unmanned turbine-powered aircraft--- and not a tiny one--- in Spain using a fuel made entirely from algae. Is there a future for this fuel? Maybe. Can it help reduce our dependence on fossil fuels? Maybe. Is it going to be used in commercial jet aircraft? Maybe. But don't look for it in the tanks of the 777 pulled up at your boarding gate anytime soon.

I don't doubt that diesel-electric is a viable marine propulsion system. But as I said earlier, there are a lot of inter-related elements to making it work, one of which is boat design and another of which is price.

Until a system can be developed and marketed for a price that a large segment of the boating population can afford, it will remain an "exotic" side-product, something that can go into a multi-million dollar Nordhavn but not into Average Joe's CHB.

I have no quarrel with the technology. If we can fly a plane on algae I see no reason why a small boat can't be run efficiently on diesel-electric power. But as with all these things, the technology's the easy part. It's the marketability that's the hard part. The components have to be produced using processes and in volumes that make it affordable. Like our algae fuel, the efficiency of the product is meaningless if it is offset by the cost to produce it, or transport it, or store it.

I have seen lots of stuff about how diesel electric systems can work in smaller boats. I've seen lots of discussions including the above post about the efficiencies, real or theoretical, these systems can bring. I have no argument against what's being said as it's not my area of expertise (or even interest).

But what I haven't seen is what it's going to cost.

The High Definition video cameras we use in our work cost approximately $100,000 apiece. Why the super high price? The market for these things is very small. And the development costs were very high. Divide the development and production costs (and profit) by the size of the market and you get a $100,000 price tag.

I think diesel electric propulsion, if it really does offer the efficiencies its proponents claim, is a fine idea. And boats like the big Nordhavn, assuming they work as advertised, will be one more step toward making this kind of propulsion more practical. But until the big production companies get on board--- Bayliner/Meridian SeaRay, Grand Banks, Nordic Tug, etc AND it is accepted by a sufficiently large segment of the buying public which is what it will take to get the big manufacturers on board, diesel-electric propulsion for smaller boats will remain an exotic "experiment."

And one other thing---- so far all the discussions I've seen about this propulsion system have been focused on moving boats very economically, which you can certainly do with small diesels powering generators. But a HUGE segment of the boat-buying population has zero interest in going slow. They want 20, 25, 30 knots. I suspect that SeaRay, for example, isn't going to be too interested in diesel-electric power unless it can be shown that they can produce the kind of fast boats their customers want with a diesel-electric drive system that's cheaper to operate, costs the same or less than a conventional diesel drive, and is as or more reliable than a conventional diesel system.

And they aren't going to re-tool their product line based on a few one-off examples of a lab-built system custom installed in a demo boat. They're going to want to see a production line delivering the volume of proven, warranteeable (is that a word?) drive systems that they can bolt into their boats.

Can it be done? Maybe. But like our algae aviation fuel, don't look for it in the showroom anytime soon.

Eric-- I have no quarrel with new systems like this being discussed.* I just don't have a lot or patience when these kinds of things start being touted as though they're not only going to change the world, but they're going to change it tomorrow at 9.00 am.* If people didn't think of new ways of doing things and then trying them, we'd all still be living in caves.* My issue is that more and more people seem to think everything is like CSI, where all the solutions should be found in an hour using technology that doesn't actually exist yet.* I guess it the half of me that's French, but I tend to very pessimistic when I start hearing people promising something for nothing.

As to diesel-electric power in my boat, no bloody way.* I love engines, I love controlling them, and I love hearing them.* No way in hell I'm going to give up my two roaring diesels for some pansy little constant-speed* generator and silent propulsion motor.* That's like offering a Harley owner a silent motorcycle.* If I wanted that sort of limp-wristed power, I'd get a damn sailboat

-- Edited by Marin at 01:40, 2007-12-29

I did not read thru all of the posts so I apologize..... You do have to watch out for propaganda put out by the companies who are trying to sell this technology. With that said, I do have a friend who has gone down this road with his sailboat...a Mason 43. He is one of those types that is more interested in putting different types of equipment on his boat rather than taking it out....we call them "gear queers". I have no idea of the specs on his system but there were all kinds of promises made. He would pay for all of the hardware and the "company"(don't remember who) would pay for the installation. Well, he took his freshly rebuilt Perkins 4108 out and put in an electric motor along with a Fisher Panda DC generator(I wanna say 144KW....maybe it was volts....dunno). One of the gimmics was that the boat could regenerate power by the freewheeling prop while the boat was under sail. In any event, all of that crap was taken out and the Perkins was put back in. I had beers with the new owner of the boat this evening. I wish I woulda picked his brain about the specifics of the system....maybe later.

Using "free" energy trapped within time? hahahahahahaha.......OK Starbuck fire up the tachyon drive----what a pile of crap!

I wish I woulda picked his brain about the specifics of the system....maybe later.

Pro boat builder (back issues on line FREE) had a good series of articles on this very subject bu Nigel Calder.

In a word FORGETABOUTIT.

FF

FF wrote:

I wish I woulda picked his brain about the specifics of the system....maybe later.

Pro boat builder (back issues on line FREE) had a good series of articles on this very subject bu Nigel Calder.

In a word FORGETABOUTIT.

FF

Click to expand...

Yep, I learned a long time ago that you can't talk people out of stuff like this. My only question was.... Why?* And the real answer is that he is a gear queer....pure and simple.* I had seen him take his boat out maybe twice in 6 years but boy did he spend money on that thing......kills me!!!

"Yep, I learned a long time ago that you can't talk people out of stuff like this. My only question was.... Why? "

Today in the crushing world of PC , I think its folks wanting to be "Better" than others by seeming greener.

AS long as political power can be gathered by fooling people and FIAT ( A UN carbon tax?)it will go on.

Most common in the boating world is the acceptance of New Speak , the "fast" trawler.

Used to be 25 to 40K was for motoryachts , but that's not PC to own.

FF

I have seen a good acceptance of electric motors tho as kickers on smaller dinks.

The ladies are sometimes intiminated by the fear of going ashore , and not being able to start the OB and get back.

The powerful , and fairly cheap small electric motor and sealed bats has made this a hassle of the past.

At a marina in CT more than one use a fishing motor as daily transport to the mooring.

FF

Marin wrote:

Until a system can be developed and marketed for a price that a large segment of the boating population can afford, it will remain an "exotic" side-product, something that can go into a multi-million dollar Nordhavn but not into Average Joe's CHB.

Click to expand...

The Island Pilot solar/diesel/electric boats are going to be very interesting, and they cost a lot less than the Norhavn.* I'm hoping to see one at the Miami boat show, but I don't know if they're on schedule (planned to be there last year).* It's disappointing that they opted not to build a full-size prototype, but rather to sell the very first hull.* Awfully risky given the uniqueness of the venture.

If the boat works as advertised I can definitely envision buying one.* Gas/diesel is only going to get more expensive, and global warming is real.*

There will always be a majority who want to go fast, but as fuel prices go up I think we'll see more and more converts to slow boating.

"I think we'll see more and more converts to slow boating."

OR we will see an end to Bloat Boats and return to the style known as "Commuters" in the late 20's.

Round bottom Semiplaining , great sea boats , modern diesels are 1 /5 or less in pounds / hp of the old engines and economy is far higher. Hulls can weigh 1/3 of the stout wooden construction.

The question is weather folks can enjoy boating with a hotel ballroom aboard.

70-80- years ago folks did .

Even the houseboats like a 65ft Trumphy were mostly long and lean.

FF

FF

I think there was a wide range of scantlings on the comuters of the 20s. Production FG boats aren't light and I belive lighter wood boats, especially the comuter types, were not unusual.

Eric Henning
30 Willard
Thorne Bay AK

I think there was a wide range of scantlings on the comuters of the 20s. Production FG boats aren't light and I belive lighter wood boats, especially the comuter types, were not unusual.

MY favorite STROLLER , a Herrishoff design of 1929 , was of std yacht construction of the time for 20K IN A SEAWAY.

Nice, with a bow cockpit , and on the after deck the couch at the transom was 4 ft wide!

Nice living , for those with some $$$.

Todays production boats with simple solid glass will be half the hull weight of the old woodies, and the aluminum or better grade , Airex , or Carbon fiber over a core will weigh half of that.

A new Yanmar ,BMW car engine marinization will put out more power at 1/3 or 1/4 the weight of the Sterlings of the early eras.

I have worked on several big tugs here in BC that were diesel-electric and I remember asking one of the engineers why. His reply was that the huge diesel engine was run at a governed constant speed which was its most fuel efficient and that the electric motor gave them instant full torque when they started pulling and object. At the time I remember thinking that it must be the way to go for these boats because the engine rooms were HUGE ! Our little motor/generators for converting the 120 VDC that the ships electrical system ran on to 120 VAC for the electronics and comms. were totally lost amongst all the switch gear and transfer panels these tugs had down there. I think the prop drive motors ran on something like 660 VDC but its a long time ago so I may be wrong on that, but it was a high voltage for sure. I am sure that similar sized tugs (straight diesel) had far smaller engine rooms than these ones.
Most of these tugs were ex WWII navy ships both US and Can. so it was used a long while back in some ships. I believe that the new azimuth steered tugs that have as much pull sideways as fore/aft are also diesel electric but again that's just my impression from watching them work. Most of the new cruise ships are also electric driven with the motors inside the prop pods.
I think that if the vessel is BIG, diesel-electric is the choice unless its straight from A to B like the big container ships etc but its not far enough advanced in small versions as yet for our boats.

John Tones "Penta"
Sidney, BC

It's interesting that after I posted the initial question about the future of electric/diesel engines, I found an article*published in Southern Boating Magaizine in January 2008, that reviewed a prototype engine built by Siemans.* The electric/diesel engine was fitted into a 42 foot trawler originally built with twin engines etc.

The trawler's twin engines were replaced with a single 225 hp engine and two electric motors.* Fuel economy improved over 10%, sound was reduced 6 dba and the system occupied significantly less space than the twins.* Slow speed handling was vastly improved and with a flick of a switch, the boat could be powered by the trawler's generator,*running 5-6 knots.

The author was so impressed that he predicts we will start seeing these units in boats as small as 30 feet,*giving more room for people aboard.

Well there you have it folks, looks like we're in for some inovation on the propulsion scene soon.

MT

Mr. Marine Trader,
There's no reason a conversion that you mention can be done and I don't doubt that savings can be had BUT how much will it cost to do such a conversion? People like me won't spend mega $$ to convert and until prices come into line that would make $$ sense to replace say a blown engine out of a twin engine boat with electric conversion, it just won't happen. I think Penta hit the nail on the head by saying diesel electrics have their place.