Dan Hollinshead converted well to put the Steamers up 7-3. Winger Tino Nemani sparked another fine attack as the Steamers confidence was clearly lifted by their fine start.
But ruck penalties conceded let Manawatu's Otere Black kick two quick penalties to regain the lead.
From the restart, the Steamers put together their best concerted attack of the season, which captain Retallick finished off with a try in the corner.
Hollinshead had two attempts at the conversion, after an early charge, but missed them both.
The Steamers had the lead 12-9 after 30 minutes play but in the final 10 minutes before the break, Manawatu scored two tries as the Steamers fell off tackles.
Fullback Nehe Milner-Skudder was a key factor as Manawatu went to halftime leading 21-12.
Steamers centre Siaosi Iongi made an early break in the second half, supported by lively flanker Johan Bardoul.
The next scrum was clearly a win for the Bay against the feed but the crucial decision went against the Steamers.
It proved costly as Manawatu broke free after a poor pass from Byron McGuigan and scored from the counter attack to lead 26-12.
McGuigan and Black swapped penalties before replacement prop Mike Kainga crashed over for a late try in the corner after more good work from Bardoul.
The Steamers finished strongly on attack, with hooker Joe Royal scoring with two minutes to play to set up a thrilling finale.
The Steamers have another three-day turnaround before they take on fellow strugglers North Harbour at Rotorua's International Stadium on Sunday afternoon.
Manawatu 29 (Nathan Tudreu, Antonio Kirikiri, Newton Tudreu tries; Otere Black con, 4 pens) Bay of Plenty 27 (Siegfried Fisiihoi, Culum Retallick, Mike Kainga, Joe Royal tries; Dan Hollinshead con; Byron McGuigan pen; Te Aihe Toma con)