Gav Sharman scored a hat-trick of tries in a second league win of the season.
Willis Ingleby (2) and Tom Wilson were also on the scoresheet as Spalding’s young backs came alive on Saturday with a display of running rugby that Grimsby could not live with.
However, the game was a tale of two halves with the visitors looking the better team for 35 minutes of the first period.
Early on Spalding were exposed with breaks out wide with support runners and only excellent cover tackles by fullback George Douglas and left-winger Sharman saved the day.
With few changes from last week, George Freeman made his debut in the front row and Taylor Crowson had his first start of the season at outside centre and John Barrett starting at hooker.
Spalding’s unity and determination was tested as Grimsby encamped themselves on the five-metre line with tackles stopping the visitors scoring.
During this period Spalding’s scrum gained the upper hand and during the afternoon Ash Piccaver worked well in the lineout, stealing the opposition ball on three occasions.
Grimsby missed a long-range penalty to open the scoring with five minutes of the first half remaining and shortly afterwards Douglas with an up-and-under kick ahead was taken out late with the Grimsby player being yellow carded.
Spalding immediately took advantage with the forwards driving upfield led by Jason Steels and Ash Anker making headway.
From the breakdown scrum half, Richard Cooke swiftly passed the ball out to the backs and Sharman outpaced Grimsby’s weakened defence for the opening try with fly-half Ingleby converting.
Then in injury-time, Spalding created a gap in Grimsby’s defence, Ingleby seized on the opportunity and burst through for his opening try and within the last few minutes of the first half Spalding had opened a 12-point margin.
At this point, Grimsby were certainly not out of the game and after 10 minutes, a 25-metre break saw them open their account with a converted try.
But Spalding’s response was immediate with the ball breaking loose deep in Grimsby territory, a pick up saw Ingleby run through to collect his second try.
The game was swinging from end to end with play becoming more open and it was Grimsby’s turn to score in the corner. With an excellent conversion, the margin was down to just five points.
Spalding responded by taking a grip on the game and as Grimsby tried to pass their way out of defence Wilson – who had come on for Dan Adams – made a one-handed interception, controlled the ball and sailed in for a converted try.
With Freeman and Anker off with knocks, Will Shields came on at scrum-half and George Berry at lock with Spalding strengthening their control.
Piccaver broke through two tackles, gained 40 metres and as the final tackles came in, he offloaded to Sharman to run in his third try of the afternoon. But Grimsby stole the final try of the day as the referee blew the whistle.
This was an afternoon when Spalding discovered the untapped ability in their young backs to win games while the forwards pack took control up front.
Another outstanding feature was their defence in the first half when under sustained pressure.
The team should now take confidence into next week’s derby trip to Kesteven.
Spalding: Hudson, Barrett, Freeman, Turner, Piccaver, Anker, Steels, Brown, Cooke, Ingleby, Sharman, Adams, Crowson, Capes, Douglas. Subs: Shields, Berry, Wilson.