This account seems to confuse Alston with Michael J. Givens:
http://64.233.179.104/search?q=cache:LTlqxgcsYp8J:www.charlotte.com/mld/charlotte/news/politics/9251042.htm%3F1c+%22david+alston%22+kerry&hl=en
Kerry took over command of Alston's boat, PCF-94, after a battle in which the boat's previous lieutenant had been injured. Alston was also wounded in that fight, a clean gunshot through the arm.
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http://www.scienceblog.com/community/older/archives/K/2/pub2117.html
29 JAN 1969 Cua Lon Rivers
Early in the morning seven swift boats embarked on a mission to destroy enemy installations along the Cua Lon River. While Kerry's boat and another (PCF72) were probing a canal along the river, Kerry's boat came under heavy fire and was hit by a B-40 rocket in the cabin area. One member of Kerry's crew -- Forward Gunner David Alston - suffered shrapnel wounds in his head. His injuries were not considered serious and he was sent to the 29th Evac Hospital at Binh Thuy.
(snip)
27 FEB 1969 Bay Hap River
On an evening patrol with two other swiftboats, PCFs 23 and 43, about 26 miles south of Ca Mu, the patrol took heavy fire, including five rockets. Three rockets narrowly missed Kerry's boat, and exploded on the opposite bank. Another rocket exploded near PCF 94, and the fifth exploded near PCF 23, wounding a crewmember on that boat. The boats suppressed the fire and withdrew. During the battle, a sailor on Kerry's boat, Crewmember/Trainee Michael J. Givens was shot in the upper right arm. Givens injuries were not serious and he was sent to the 79th field hospital in Can Tho.
Early in the morning seven swift boats embarked on a mission to destroy enemy installations along the Cua Lon River. While Kerry's boat and another (PCF72) were probing a canal along the river, Kerry's boat came under heavy fire and was hit by a B-40 rocket in the cabin area. One member of Kerry's crew -- Forward Gunner David Alston - suffered shrapnel wounds in his head. His injuries were not considered serious and he was sent to the 29th Evac Hospital at Binh Thuy.
Kerry was not on the boat at this time. It was Peck I believe.
Early in the morning seven swift boats embarked on a mission to destroy enemy installations along the Cua Lon River. While Kerry's boat and another (PCF72) were probing a canal along the river, Kerry's boat came under heavy fire and was hit by a B-40 rocket in the cabin area. One member of Kerry's crew -- Forward Gunner David Alston - suffered shrapnel wounds in his head. His injuries were not considered serious and he was sent to the 29th Evac Hospital at Binh Thuy.
As much of this story as I can figure out, this was the engagement when Alston and his OIC, Lt. Peck were both wounded on PCF-94. kerry replaced Peck after he was wounded. Had it been kerry's boat, he would certainly have been wounded when the B-40 hit the cabin area. kerry wasn't wounded but Peck was.