History of Diesel Displacing Steam in U.S. Merchant Marine

The D7’s were suppose to be 21 knot ships. I just happened to be in the office when the results of sea trails came in and there was a lot of disappointment and consternation. SeaLand sued Bay Ship for not meeting design specs.

It is all about horsepower and hull form that determine a ships speed, not the prime mover.

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Of course it’s about horsepower, no question. Not saying the steam ship are faster in theory.

I was saying maybe it was capital cost vs operational cost. In other words maybe the steam plant had more hp per dollar in capital cost. But operational costs were higher because of fuel consumption.

That’s what the analogy of Tote ships to the 70’s muscle cars implies. It was cheap horsepower.

Assuming steam is better $ per HP than spending just a little more on a bigger steam plant to get more margin to meet specs makes more sense than having to make the big step from a 7 cylinder to an 8. The guys building diesel ships are going to use a sharper pencil to calculate HP required.

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Actually there isn’t much difference in the capital costs between a steam plant and a diesel plant. It is all about the operational costs. Before automation came into greater play the crew sizes (and costs) were the same. Motor ships were always more fuel efficient than steam plants of equal size & horsepower. Maintenance costs however are significantly greater on a diesel plant than a steam plant. Pistons, rings, cylinder liners and such are considered consumable spares. When fuel was cheap (a few dollars a barrel) the cost differential in consumption on a steam plant was less than maintenance cost differential which made steam plants a viable option. (It didn’t help that there were no large low speed engine licensees to manufacture engines in the US).

When the cost of fuel went up 10 fold in the 70’s steamships quickly became uneconomical compared to motor ships. Greater automation and unattended engine rooms allowed crew cost to enter the fray giving motor ships an even greater advantage.

Agreed, as long as there was cheap fuel.


It’s sounds like everything you’re saying is right. But I don’t know, seems like something is missing.

When I say steam ships seem faster I don’t mean in a technical sense. I mean to say that when I first sailed on U.S. ships in the traffic of the Far East we were almost alway the fastest ship around, almost never overtaken.

It seems like diesel replaced steam starting wth the smallest ships and then gradually displacing the plants on the larger ship. In that case there would have to have been a time when there would have always been ships in between where either choice made sense.

That is to say at any given point during the transition large ships would need steam and small ships would use diesel. In the middle the builder had a choice. They had to choose between economy and speed.

On the other hand, maybe it was higher labor costs on U.S ships at the time that caused the U.S. ships to stick to steam longer.

What needs to be taken into account and included in the discussion is the evolutionary path of increasingly larger steam plants and diesel engines. I sailed on WW2 built ships and they were 450 psi sectional header boilers. From there I moved onto 600 psi and finally 1000 psi boilers. Steam plants moved up the developmental path quicker than their diesel counterparts.The largest single diesel engine built up until the early 1960’s was a B&W engine of 22,000 hp. The footprint of that engine today would have 3 to 4 times the horsepower. It took some time for the diesels to catch up, but catch up they did if you look at what is being produced today.

In actual use; I recall beating a typhoon on old Pacer Class container ship. Chief put in bigger tips and we were flying along. Chief was grumbling about fuel consumption. That’s it.

Try running at speed on a diesel, say in pirate country.

First you have to discuss with the chief the max allowable rpm. The book says 96.5 but the chief only wants to run 95.

Ok fine, 95. Next you get a call, # 7 cyclinder is running hot, got to take a turn off, now 94. Six hours later now the sea temp is too high, got to take a turn off, now 93.

As so forth, Don’t recall that happening back in back in the day.

Without a doubt you have much greater operational flexibility with a steam plant. Moving from steam to diesel or vice versa is an apples to oranges thing and requires a different operational mind set.

Yes, but in this context. In the year 1950 if a fast ship was going to be built it was going to be steam. In some years after 1950, upon learning that a ship was going to use steam in many cases it was safe to assume it meant a fast ship was being built.

In some time period between 1950 and now that stopped being true.

The author is saying that in the mid 1970’s, upon hearing the ships Sun Shipyard were building were going to be steam, people assumed they were going for speed rather than economy.

For the most part I agree with what you are saying. I would say worldwide steam still ruled in 1950 though not 100 percent. In the mid 70’s I sailed on a Delta Lines ship whose C/E crossed over from Chief Diesel to Chief Steam. A real oddity at the time I thought but there were a few WW2 era ships built that were motorships that were later run by commercial companies.

The hand writing was certainly on the wall in the 70’s when the price of oil jumped. But any ship delivered had its machinery on order a year or 2 before construction even commenced. The last LASH ship built was delivered by Avondale in 1980 was steam. Really should have had diesels in them but too much was in the pipeline and Waterman was slow to change. Same goes for the RO-RO’s Waterman built in 1983 at Sun and Quincy that became preposition ships for the government. The next ships Avondale delivered in 82/83 were the C9 class containerships for APL and they were diesels.

So while the handwriting was on the wall in the 70’s the transition didn’t occur until the 80’s in the US. By that time, with the exception of LNG tankers, the rest of the world had already made the switch.

From the point of view of a mate sailing deep-sea in the 80s and 90s, diesel < 20 kts, steam > 20 kts. Till the I caught a D-9 mid 90s, average speed Kaohsiung to LB, 21.0 kts.

I need to point out that most all these ships were are discussing here were built with Construction Differential Subsidies from MarAd who placed many requirements upon the design and outfitting of them. In those days, WWII was not too far in the rearview mirror when a great many US merchant ships became naval auxiliaries

I have heard that the Navy was one of the biggest reasons that the US stuck with steamships long after the rest of the world abandoned them… The hidebound Navy simply didn’t know large slow speed diesels and didn’t want then in their fleet.

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Your point may hold some water but perhaps not as much as you think. The US and its Navy certainly have a long history with steam but not all the ships built in WW2 were steam. The Maritime Administration did build some that were motorships. Companies after the war used them commercially. The Navy was not adverse to their auxiliaries being diesel. The Sealift tankers built in 1974 had an Enterprise as its main engine. The Kaiser class oilers had Colt-Pielsticks. As there weren’t any licensees to build large low speed diesels in the US then (or now) it is hard to say what may have happened if they were available. The Navy does have a US build requirement and those were the largest engines available.

In the 70’s outside of their nuclear powered ships the navy began using gas turbines to power their capital fleet though they still had steam powered ships in their inventory.

The sts W. Alton Jones, callsign ELLT, was built in the US in Newport News and owned by the Liberian daughter of the Cities Service Group, the Grandbassa Tankers Company. It was flying the Liberian flag and van Ommeren Rotterdam managed the ship, also provided the Dutch crew. In those days this was a very large and also fast (20 - 21 knots) ship. Oil consumption at this speed was huge, about 110 ton per day.

I sailed on the ship for 14 months, the only voyages we made was from Philadelphia to Mena al Ahmad in the Persian Gulf and vv, rather boring to say it politely. Loading in Mena took 12 hours and discharging in Philly 24 hours. On top of that after the Suez Canal crisis we had to sail around Cape Good Hope. We did that non stop with extra bunkers in cargo tanks. A round trip took six weeks with no leave in Mena and only 24 hours in Philadelphia. It is true that we were never overtaken by other ships on that busy route.


Quite a wake at 21 knots. It seems that half the shaft power is lost in that wake,

What I remember is that the ships, we were with four ships also the Statue of Liberty, the Liberty Bell and the Cradle of Liberty, were heavily subsidized by the American government so that they could function as Baby Flattoppers, hence the speed of 21 knots.


That’s me, at a young and tender age, on the top deck next to the emergency steering wheel and the magnetic compass.

Every now and then the Bailey board went berserk causing alarms so loud that some were desoriented. False alarms occurred too frequently. Sometimes one of the boilers tripped, we said then that it had ‘fallen of the board’.


Here are the specs for the Cape Jupiter, built at Bath Iron Works for States LIne in 1976.


I was third mate on a sister ship. I was on watch one day and I was standing in the corner with my binoculars looking aft. Capt comes up the bridge and see me and asks “What’s going on?” I told him that we were being overtaken by another ship. He come over and looks and then says “Well, it’s going to take them a long time.”

I recall we were running about 19 kts or so at the time.


Yes, the US built diesel powered vessels during the war but not many were motorships. Mainly C1’s and C1-M’s with a single lone Victory class ship being fitted with a very large Nordberg. The biggest thing about these vessels was that they lacked the speed which a liner was expected to operate at. After the war ended any slow speed diesel industry simply withered away very fast as any new construction was fitted with steam plants and I still hold that a large reason for that was that the Navy wanted any auxiliary to be able to make more speed than any diesel plant could obtain.

btw, here is a photo of that one Nordberg fitted to the EMORY VICTORY

as far as any Colt Pielstick powered ship…they are not slow speed and thus do not count!

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Don’t forget there were the C3-M class. Four were built, SS Mormacpenn, SS Mormacyork, SS Mormacland, and the SS Mormacmail. The MORMACPENN, launched 10 November 1939, was the first to be completed and sailed from New York in early February 1940 for the East coast of South America. She was described as the fastest cargo liner ever built for American-flag operation, for prior to her entry into service she reached a trials speed of 19.7 knots and when northbound from Baltimore to New York for loading she did over 20 knots for a time. Propulsion was by four 7-cylinder, two stroke cycle, Busch-Sulzer diesel engines, driving a single screw through electro-magnetic couplings and reduction gears. The ship could be operated with any combination of the four engines, on one at 25% capacity or all four at 100% capacity. The Navy took them and converted 2 to sub tenders and 2 as escort carriers.

The same basic design was used for the Avenger class escort carriers, Four were built with 3 going to the Royal Navy and the US getting 1.

The point being, they weren’t all steamships.

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actually you taught me this time…I had not known that these additional motorships were built. I thought every single C3 was built as a steamer.

The SL7’s were real beauties. I attended the sea trials of the three built in Holland, the Sea-Land McLean, Resource and Exchange. The first one delivered by the RDM Shipyard in Rotterdam in 1973 was the Sea-Land Exchange. With 120.000 hp in their belly they did 33 knots. During the trials they even pushed it up to 36 knots as could be seen on the Ametek Straza doppler SOG log. I remember that during those trials on one ship, when it made a sharp turn, the entire buffet fell on the floor…

Malcolm McLean made a couple of mistakes, already the market was changing from 35’ to 40’ ft containers. The size of the 35 ft container was dictated by road transport limitations then. Furthermore the fuel prices were already rising and 2000 TEU was a much too small number for all that engine power. Present day Short Sea feeders are approaching already that number of containers. In short they were not economical and were acquired by the US Navy in October 1981. I am curious if they are still around in that mothball fleet, all steam and probably almost nobody around who can operate them.


I sailed on the MCLEAN back in 81. They are still around, but modified into ROROs for military purposes in the Ready Reserve Fleet. https://en.wikipedia.org/wiki/SS_Capella_(T-AKR-293)

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Google fast sealift ships