“The Metal Shark 75 Defiant Patrol boat, capable of achieving 40+ knots. For the ideal balance of performance, economy, and reliability, twin Caterpillar C32 diesels mated to Hamilton HM-651 waterjets will propel the vessel to speeds in the 30-knot range.” Photo via DBA METAL SHARK
gCaptain is reporting that the US has pledged $18M to help Vietnam buy US made patrol boats. gCaptain does not specifically state which boats will be bought or how many, but the choice of illustration above certainly suggests that they will be Metal Shark 75 Defiants. There is more information on this boat here.
Chuck Hill's CG Blog 
The Japanese are helping too. This from the German Navy blog, Marine Forum, “August 10, VIETNAM, The Vietnamese fisheries department received a second of a total of six former Japanese surveillance vessels … (former) name HAYATO, 56 m, 1,080 ts, built in 1993 …. „non-refundable aid“ … first delivered in February, remaining four to follow later this year.
A bit more detail here: http://thediplomat.com/2015/08/japan-gifts-vietnam-patrol-vessel-amid-south-china-sea-tensions/
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Latest transfer. Boats but also a lot of supporting equipment. https://www.marinelog.com/index.php?option=com_k2&view=item&id=28879:metal-shark-delivers-second-series-of-patrol-boats-to-vietnam&Itemid=223