for Submariners

by Hamilton 1:1 Communications, LLC

Greater Underwater Propulsion Power Program
Guppy II

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Guppy II Program

The GUPPY II conversion (SCB 47), implemented from 1947 to 1951, was generally similar to the GUPPY I, except for retention of both periscopes and introduction of the recently perfected snorkel. The addition of three new masts; snorkel induction, snorkel exhaust, and ESM mast -- required more room in the upper portion of the sail. BuShips approved two different sail designs:

1) The "Electric Boat Sail" had a straight trailing edge, round windows, a wider top and a more rounded forward edge.

2) The " Portsmouth Sail" had a thinner top, curved trailing edge, square windows and a sharper lower forward edge. It was put on all boats, which used the government plans for the conversion.

Some boats with a Portsmouth Sail had an SV radar and needed extra room to house the aerial, thus had a bulge at the sail top. Later modifications put the SS or SS2 radars on these and other boats which had a smaller aerial and had an indicator with interlocks which allowed the mast to be housed only with the aerial in certain angular positions. Also, some GUPPY II and GUPPY III boats had their sails extended higher above the waterline, the "Northern Sail", to raise the bridge, allowing it to be manned in more severe weather.

All boats converted during the GUPPY II program that originally had high-speed drive motors with reduction gears had these replaced with low-speed direct-drive motors, producing 2500 horsepower (1.9 MW) per shaft.

The two GUPPY I boats, Odax and Pomodon, were modified to GUPPY II standard.


Boats Converted:

USS Catfish (SS-339) (Balao)

USS Clamagore (SS-343) (Balao)

USS Cobbler (SS-344) (Balao)

USS Cochino (SS-345)
USS Corporal (SS-346) (Balao)

USS Cubera (SS-347) (Balao)
USS Diodon (SS-349) (Balao)

USS Dogfish (SS-350) (Balao)
USS Greenfish (SS-351) (Balao)

USS Halfbeak (SS-352) (Balao)

USS Tiru (SS-416) (Balao)


USS Tusk (SS-426) (Balao)

USS Cutlass (SS-478) (Tench)
USS Sea Leopard (SS-483) (Tench)

USS Odax (SS-484) (From Guppy I)

USS Odax (SS-484) No. Sail
USS Sirago (SS-485) (Tench)
USS Sirago (SS-485) (Tench Southern Sail)

USS Pomodon (SS-486) (From Guppy I)

USS Volador (SS-490) (Tench)

USS Amberjack (SS-522) (Tench)
USS Amberjack (SS-522) No. Sail (Tench)

USS Grampus (SS-523) So. Sail (Tench)
USS Grampus (SS-523) No  Sail (Tench)

USS Grampus (SS-523) Aerial View (Tench)

USS Pickerel (SS-524) (Tench)
USS Grenadier (SS-525) (Tench)




307' 7" length
27' 4” Beam
17' Draft
2,040 tons Surfaced Displacement
2,400 tons Submerged Displacement
4,610 SHP Diesels, 2 Shafts
4,610 SHP Electric Motors, 2 Shafts
18 kt surfaced speed
17.5 kt submerged speed
15,000 nm at 11kt surface endurance
192 nm at 4 kt submerged endurance
400 ft Test Depth
84 to 85 crew


6 x 21” TT Bow
4 x 21” TT Stern
24 x 21” Torpedoes