BOSTON — Where have all the home runs gone?

David Ortiz was good for one home run every 10.3 at-bats last year, adding up to a Red Sox record-setting 54 round-trippers in 558 at-bats in 2006. Manny Ramirez produced a homer every 12.8 at-bats, adding up to 35 dingers in 449 at-bats.

This season? There has been a decided power outage from Boston’s dynamic duo.

Ortiz has only 11 homers in 223 at-bats, one every 20.3 at-bats. Manny has a mere 8 blasts in 235 at-bats, averaging one every 29.4 at-bats.

And since May 6, when they each went deep in a game on the road against Minnesota, Ortiz and Ramirez have each hit only two apiece — Ortiz in 101 at-bats, Ramirez in 115 at-bats.

But don’t blame just Ortiz and Ramirez for their low home run totals.

Take a look at the top of the order and its inability to get on base over the last several weeks, prior to last night’s J.D. Drew-Dustin Pedroia bonanza (a combined 8-for-9 with 8 RBI).

Take a look at how Ortiz and Ramirez are being pitched, especially when there’s no one on base when they step into the batter’s box, with recently deposed leadoff man Julio Lugo struggling (.270 on-base percentage) hitting in front of them.

Kevin Youkilis had a .418 OBP, fifth-best in the league, but he has been moved all around the batting order, plucked out of his number-two role a fair amount the past few weeks to try to shore up other holes in the lineup. So Coco Crisp (.280 OBP) has hit second a few times before manager Terry Francona began juggling that part of the order.

And who’s been hitting behind Ramirez most often? Drew, who, while his on-base percentage is decent (.336), was batting only .230, so why give Ortiz or Ramirez anything to hit with those other circumstances — no one on base and no protection in the number five hole?

Neither player added to his home run total last night. Ortiz went 0-for-1 and was ejected for throwing his helmet and bat in the direction of plate umpire Tony Randazzo after he had been called out on strikes in the first. Ramirez went 0-for-3.

Earlier in the day, while Ramirez, as is his wont, wasn’t available to discuss the power shortage, Ortiz tried to cast a realistic light on why the homers haven’t been coming for the duo as often as in the past, which has helped lead to a lack of runs overall lately for the Red Sox.

“People talk about me and Manny not hitting home runs, but if we don’t get pitches to hit, how are we going to drive the ball?” asked Ortiz.

Ortiz couldn’t address Ramirez’s homer drought, but he did try to put his relatively low total in perspective, especially given his other impressive offensive numbers.

“My OBP is higher than ever right now (.448, leading the league) and even if I’m not hitting homers, my slugging percentage (.595, third in the league) is good,” said Ortiz, who was batting .333 prior to last night’s game.

“It’s not easy to hit home runs. I make it look easy but it’s hard, especially if you don’t get a pitch to hit. They don’t pitch to me. They don’t challenge me anymore. They don’t throw fastballs to me. Have you watched how they pitch me? Away, away, away. If they come inside at all, it’s a mistake. They don’t care about walking me. It’s like, ‘Here, take your walk.’ It’s not like you’re going to steal second. I can’t do anything about that, bro,” said Ortiz.

One reason the opposition doesn’t mind walking Ortiz, especially during the Sox’ offensive slump the last three weeks, is obvious, he said. Over his last 17 games, Ortiz is batting .381 over his last 17 games, but has only 6 RBI, two of them coming on solo homers.

“I’ve been hitting with no one on base for a long time. I’m not talking smack about my teammates. Believe me, I’m not. They’re trying hard to get hits like we all are. But when me and Manny (batting .422 over his last 19 games, 6 RBI over that stretch) come up and there’s no one on, they’re not going to give us something we can drive,” he said.

While Ramirez has had the benefit of at least Ortiz being on base in front of him, Ortiz hasn’t had the bases clogged with runners when he gets up. And regardless, he sees fastballs seldom.

Take an at-bat Wednesday night against Colorado. Ortiz was up with a runner at first, none out in the fifth and the Sox down, 6-2. The count went to 3-and-0.

“Finally, I figured I’d get a fastball,” said Ortiz.

Wrong. Josh Fogg threw him a 3-and-0 changeup. Ortiz blooped a single off the end of his bat into center.

“They won’t even throw me a fastball then,” said Ortiz. “A changeup. I’m like, ‘No way.’  ”

Other pitchers have tried different patterns against Ortiz. The Angels’ right-hander John Lackey, for instance, threw Ortiz only curveballs — 13 — in three at-bats in a game in April. Cleveland’s Aaron Fultz, a lefty, threw 10 breaking balls in one key late-inning at-bat, leaving one inside that Ortiz hammered foul past the right-field foul pole before retiring him on a soft liner to third on a pitch down and away.

Ortiz, to his credit, has not gone out of the strike zone to chase pitches very often. He is patient at the plate, willing to take his walk. He had 45 bases on balls, the third-highest total in the league. And he has taken those outside pitches to left field for hits.

“I’ll slap pitches there, but it’s not where I can drive the ball,” said Ortiz.

“I want to hit home runs, but it’s not like I’m getting stuff to hit and I’m missing it. When I get my pitch I have to hit it. But if they don’t throw you a strike, you can’t hit home runs. But if they throw me a strike, I’ll get you,” Ortiz said.

skrasner@projo.com