for Submariners

by Hamilton 1:1 Communications, LLC

Greater Underwater Propulsion Power Program
Guppy III

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Guppy III Program

The GUPPY II conversions suffered from very cramped internal conditions due to the four-battery configuration. The GUPPY III program (SCB 223) was devised to address this problem. In 1959, Tiru became the prototype conversion. She was cut in half and lengthened with a 12.5 foot (3.8 m) section forward of the control room to create space for a new sonar room, berthing, electronics, and storerooms. The removal of the sonar room from the forward torpedo spaces allowed an increase in the number of reloads. Crew spaces were also refurbished. As in the GUPPY IIA conversion, one diesel engine was removed.

From 1961 to 1963, eight more GUPPY II boats were upgraded to GUPPY III standard. These boats differed from Tiru by adding a 15 foot (4.6 m) section forward of the control room. They also retained all four diesel engines. This increased the boat's length to 322 feet (98 m) and raised surfaced displacement to approximately 1975 tons.

All boats received the BQG-4 PUFFS passive ranging sonar, identifiable by the three fin-like sonar domes added to the superstructure. The conning tower in the sail gained an additional five-foot (1.5 m) section to accommodate the Mk 101 fire control system and Mk 37 director. All GUPPY III boats received a plastic sail.

The GUPPY III conversion was part of the Fleet Rehabilitation and Modernization (FRAM) program. All 24 GUPPY II boats were originally slated to receive the GUPPY III upgrade, but budgetary constraints limited the program to a total of nine boats. Despite their extensive modifications and upgrades, the GUPPY III boats served only slightly longer than the rest of the GUPPY fleet.

Except for the USS Tiru SS-416, Guppy III conversions removed one diesel engine to accommodate more A/C capacity and a larger fresh water distiller.




321' length
27' 4” Beam
17' Draft
1,975 tons Surfaced Displacement
2,870 tons Submerged Displacement
5,400 SHP Diesels, 2 Shafts
4,610 SHP Electric Motors, 2 Shafts
17 kt surfaced speed
16 kt submerged speed
15,900 nm at 8.5 kt surfaced endurance
108 nm at 4 kt submerged endurance
400 ft Test Depth
83 to 95 crew


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


BQS-4 active search sonar
BQR-2B passive search sonar
BQG-4 passive attack sonar