ATV and snowmobile maker ­Arctic Cat Inc. said Thursday that it missed earnings and sales targets for the fiscal third quarter as a new partnership with Yamaha lowered profit margins.

The Plymouth-based manufacturer also lowered its 2014 financial forecast, causing shares to sink more than 21 percent in midday trading before recovering somewhat to close at $47.82, down $5.91, or 11 percent.

“We expected the second half of our fiscal year to be challenging,” said CEO Claude Jordan during a conference call Thursday. “Profitability in the 2014 third quarter was reduced chiefly due to anticipated lower gross margins on snowmobile models built for Yamaha as part of our new partnership this year, and due to ATV product mix.”

Under the new agreement, Yamaha supplies Arctic Cat with its top-of-the-line four-stroke snowmobile engines, while Arctic Cat builds its well-regarded snowmobile chassis for Yamaha. However, the Yamaha products sell for less than Arctic Cat products, which affected profit margins.

The first large shipments went out during the fiscal third quarter, which meant the margin impact was “primarily absorbed” in just the third quarter, Jordan said.

The margin change, which compared unfavorably with Arctic Cat’s earnings results for the same period a year ago, was anticipated and is not expected to affect future quarters to the same extent, Jordan told analysts.

What wasn’t expected was the drop in Canadian currency value and lower-than-anticipated ATV sales growth. ­Officials originally expected ATVs and side-by-side vehicles to grow more than 20 percent.

Despite those challenges, Jordan said the company expects “strong fourth-quarter sales and earnings” amid enhanced cost controls and ramped-up shipments of Arctic Cat’s new and narrower Wildcat Trail ATV.

Robert W. Baird analyst Craig Kennison said that “in dealer checks, we hear a lot of enthusiasm about your new products. They are excited about those products” which include new Wildcat sports ATVs, a new four-seater ATV, and a narrower ATV that can better navigate park trails. Kennison noted that new-product sales are rising, but it appears that sales of Arctic Cat’s older models may be starting to lag.

The company lowered its forecast for the full fiscal year that ends March 31. Retiring CFO Tim Delmore said Arctic Cat now expects 2014 earnings of $2.90 to $3 a share, down from the prior forecast of $3.27 to $3.37 a share. Sales are expected to reach $740 million to $750 million, down from the forecast of $754 million to $768 million.

Overall earnings for the fiscal third quarter that ended Dec. 31 fell 33 percent to $12.1 million, or 89 cents a share. That was far below the $1.32 per share consensus estimate of Wall Street analysts. Sales rose 3.5 percent to $225.8 million from a year ago but also fell short of the $241.6 million analysts expected.