West Ham fell behind in the fifth minute but hit back to be 3-1 ahead by half-time, as a Manuel Lanzini penalty, Craig Dawson’s header and a thunderbolt from Scamacca put them in control.
Silkeborg pulled one back in the 75th minute, but West Ham held on to maintain their perfect start in the Europa Conference League after two games.
Scamacca’s strike was the highlight of the night, with the Italian now on three goals for his new club since joining them for £35.5million from Sassuolo in the summer.
“I think we are beginning to see a little bit of that [his ability],” said Moyes. “I was a bit disappointed in his early performance, I wanted him to hold the ball up better.
“I thought he grew into the game, and he got better in the first half, but we are still bringing him back, we are still getting him used to it. But he has got that [the strike for the goal] in abundance, and I am hoping he shows much more of that to come.”
West Ham have so far struggled for form this season as it has taken time for Scamacca and other new signings to bed in.
Their performance against Silkeborg was a mixed one, with the Hammers impressing at certain moments but failing to kill the game off when they were 3-1 up.
“Bits and pieces I liked, bits and pieces I didn’t,” said Moyes. “We have to give them credit. But when it was 3-1 we should have been comfortable and we had other chances to make it 4-1 or 5-1 in fact, and we didn’t. That was always going to make it nervy.”
West Ham are now in a commanding position at the top of their group, with Anderlecht, who they face next on October 6, two points behind them in second.
FCSB are five points behind the Hammers in third and Silkeborg are bottom of the group, having lost both their games.
“We did it well in the Europa League last year where we really went quick out of the group and we want to do the same here,” said captain Declan Rice.
“Obviously the next game is tough, but we will be ready. We want to close the group as soon as possible. We are confident, and you can see now we are starting to click as a team.”