=> Da Noli
Freighter 1:480 - aka: Benledi
Rajens' List's codes describe this as a "Cold (War)...Cargo liner", which I guess is another way of saying a modern (i.e., post-WWII) freighter. Anyway, that's what it is (I have one and I know), and I list it first because it has a beautiful, full hull - looks very accurate - distinguishing it markedly from the bulk of the other Revell "Flat-Bottom Boat" merchantman molds (see below) - even though, according to Rajens', the "kit dates back to about 1968". Likwise, they suggest the last release was "circa 1991", by Revell-DE. That could well be, but I had no trouble picking one up over a full decade later than that.
Hospital Ship - aka: Hope, Repose
Though not technically a merchantman, still this is a utilitarian vessel which "has the look" - and another, rare example (for early Revell) having a just gorgeous full-hull. Rajens' List says it dates "back to around 1955", and was "re-issued under the SSP program in 1996". Though I haven't seen any re-releases, what I have seen is very plentiful availability on eBay (under all three names, above) - so there must have been a ton of them distributed.
=> Hawaiian Pilot
Freighter 1:380 - aka: Doctor Lykes, Matson Line freighter, C-3 freighter, C-2 freighter
This is a classic Revell "Flat-Bottom Boat"; not bad above the waterline (though dated and rather simple) - and extending significantly below as well - but then going completely flat just before the turn of the bilge. Not too much work for a waterline build - substantially more so to make it full-hulled. Rajen's claims the mold dates from "circa 1961", and that Revell-DE planned to re-issue it, as Hawaiian Pilot, in 2005 - and indeed I did pick one up exactly as such, earlier this year. They also claim close comparison with the very similar-looking Haskell-class attack transport (APA) - likewise a Flat-Bottom Boat, released as Montrose, Randall et.al. - definitively proves that neither mold is derived from the other. You sure could fool the casual observer, though!
Attack Transport 1:380 - aka: Randall, Burleigh
This is the Flat-Bottom Boat attack transport (APA) mold which looks so similar (superficially, at least) to the Hawaiian Pilot/C3 freighter, above. According to Rajens' only Burleigh, actually a Bayfield-class APA, had a C3-type hull; the Montrose and Randall being Haskell-class ships, with VC2-S-AP5 hulls. All of which only goes to show, IMHO, that these hulls were all so similar - and Revell's dimensions for them accurate enough - that the difference is pretty unnoticeable. Rajens' claims the mold was originally issued as Randall circa 1956, however my own experience is that by far the most common variant - including Revell-DE's latest re-issue, which I snagged about 3 years ago - is boxed as Montrose. This kit was also extensively sold under the brand Advent.
=> Mission Capistrano
T2 Tanker/Oiler 1:380 - aka: Glasgow, British Sovereign, J.L. Hanna
Again, a Flat-Bottom Boat - except the below-waterline extent is nothing near as deep as the turn-of-the-bilge on the real thing. Rajens' lists it as a "Cold (War)" vintage, but it looks to me of significantly earlier design than that; would look just great alongside your Montrose, above, for example. The original issue, according to Rajens', was as the civilian J.L.Hanna, in 1955 - and indeed the latest re-release, again by Revell-DE, is boxed as the civilian Glasgow. It seems to me I have also seen some pretty recent boxings as British Sovereign as well. Still, since 1964 (according to Rajens') a very numerous variant - and again, I have seen this personally - is the military Mission Capistrano - which includes a few additional parts in the form of guns and tubs for them. This was another which was re-released in some quantity by AHM, an example of which I have.
=> Pine Island
USN Seaplane Tender 1:400 - aka: Currituck, Norton Sound
Again, a military craft - but with such obvious "working vessel" lines as to deserve mention here (and in fact, may quite possibly be the closest thing in this scale to the oceangoing tug you're seeking, Jim). Again, it is another Revell Flat-Bottom Boat - and another whose draft, like the T-2 tanker above, does not extend (even close) to the turn-of-the-bilge. According to Rajens', the original issue was in 1956 as Norton Sound; a missile-test ship - including different parts than in the seplane tender variants first boxed 10 years later. Over the decades, by far the most prevalent boxing appears (in my own experience) to have been as Pine Island. I believe I have also seen a fairly recent Revell-DE re-release of this mold - and it was defiinitely included very recently (as Currituck, IIRC) in the commemorative "Guided Missile Fleet" re-release - but together these must still not have been too extensive, as you don't see it around that much, nor at bargain prices.
Nuclear Freighter 1:380
This is another mold with beautiful, full hull - and, according to those who know (including Rajens' List), also the most accurate of the several distinctly different molds of this ship, in around this scale, by several manufacturers - truly a remarkable achievement for "around 1958", the initial release date claimed by Rajens'. I only list it last because its sleek, futuristic lines are much more evocative of a passenger liner than the more utilitarian-type ships about which the most interest was initially expressed. Although Rajens' List refers to a "recent Revell-Germany issue (kit #) 05235", I have seen zero evidence of it anywhere - suggesting that the more numerous distribution dates from Revell's "1980s 'History Makers' series as kit 8622". I do not have an example of this kit, but I do have the only slightly (8%) larger Glencoe mold; in 1:350 scale, and it looks pretty darn nice - maybe a more available/economical target to seek out on eBay.
So that's what I come up with - just for Revell - on merchantmen, circa 1/400-1/500; I hope it helps. Revell has several more as well, at larger scales still. And please don't tell me you're interested in passenger liners too - for then I will be forced to also tell you about:
# S.S. Brazil - Moore/McCormack Liner 1:420 - aka: Argentina
# Finnjet - Silja Line Ferry 1:400
# Queen Mary 2 - Cunard Liner 1:400
# Titanic - White Star Liner 1:400
# Titanic - White Star Liner 1:570
# Queen Mary - Cunard Liner 1:568
# United States - US Liner 1:600
Now, who has more - and what manufacturer(s) do you want to investigate next?