It puzzles Tankmar Horn that the United States allows the Great Lakes to freeze solid for three months of the year, halting shipping and slowing industry through-out the upper Midwest.

"We've never understood that," he says with a hint of Finland in his voice.

When the arctic winter plunges northern Scandinavian into a season of binding white snows and deafening darkness, Finnish ports and waterways stay open. Channels are smashed through the frozen Baltic Sea by a fleet of icebreakers.

Hornis the ic chairman and chief executive officer of the Finnish company that makes icebreakers, Wartsila, which is better known in this country for its Arabia glassware.

For tow weeks Horn has been in the United States, hoping after a 13-year effort to sell his first icebreaker here.

The costomer is Congress, which this fall will consider supplemental appropriation for the Coast Guard to buy a Finnish icebreaker. The Coast Guard is not pushing for the Finnish ship, preferring like the other uniformed sevices to build its own craft.

But Horn said a breakthrough in gaining Coast Guard acquiescence could come with another shipbuildng job for which bids were opened recently. Wartsils' $18.5 million bid to a Coast Guard cutter was $14 million below the nearest domestic shipyard.

"Perhaps after seeing one of our ships, they will feel different about us," he said Friday before a final day on Capital Hill with former U.S. Ambassador to Finland Mark Austed at his side.

Wartsila's shipbuilding division is the world's largest maker of ice breakers and the only shipyard specializing in them. Since World War II Wartsila has made 42 icebreakers which now carry the flags of Scandinavian countries, Russia, and Argentina.

But the company has yet to crack the United States market, and that is a sore point with many Finns, noted Austed. Not only does Finland have a severe balance of payments deficit to the United States - importing about twice as much as it exports - but there is an emotional need to be recognized more than Marimekko fabrics, he said.

"Everyone in Finland understands the importance of icebreakers," Horn explained. "They mean as much as a car to the rank and file American."

Without icrebreakers, Finland's economy would freeze in November and not thaw again until April, casuing disruptions far more severe than the winter suspension of grain, iron ore and coal shipments on the Great Lakes.

The same icebreaking techniques that keep the Baltic Sea and the Gulf of Bothnia open could easily bring year-round shipping to the Great Lakes, Horn contends.

Austed estimates 60,000 American jobs are lost for the winter when Great Lakes shipping ends, and calculates the economic impact on business and employment at $16 million a week.

"Multiply that times three months and you could pay for an ice-breaker in one year," added Austed, whose tour as ambassador made him an ardent believer in Finnish icebreakers.

The icebreaker the Finns want to sell the U.S. is a $55 million vessel that measures 343 feet long and 78 feet wide. Its chief icebreaking weapon is brute force. The 22,000 horsepower engines power four screws, two in front and two in back, allowing the ship to ram repeatedly and repidly into ice floes. The slopping bow rides up and over ice ridges, crushing them beneath the ship's weight.

A Wartsila-developed "bubbler" forces a lubricating flow of water between the ship and the ice, making passage casier, Horn explained. When ice pinches its flank, the ship can rock itself loose by rapidly pumping water from tanks on one side of the ship to tanks on the other side.

Five similar vessels have already been built and an American version could be turned out in two years at a fixed price, the shipyard executive said.

The Finns are pressing for an American order now in part because their critical shipbuilding industry faces severe layoffs unless new orders are found soon. Some workers have already been laid off since ship orders began weakening last year, Horn said.

The jobs that would be created in Finland by building an icebreaker would be only a fraction of the jobs created in this country by using the vessel to keep open the Great Lakes, Austed maintained.

A coalition of Great Lakes states congressmen, some of them icebreaker advocates for a dozen years, have pushed through an authorization fot the Coast Guard to test such a vessel and are now seeking the funds to buy it.

The Coast Guard is drawing up specifications for the icebreaker and is under Congressional pressure to avoid the difficulties of its last icebeaker project.

That project - involving ships designed to explore the Artic - Ocean ran up massive cost overruns and delays before the sister ships Polar Star and Polar Sea were launched, Austed said.

The Polar Sea has been tied up in Seattle for more than a year with propeller shaft troubles, he note. And the Polar Star got stuck in the ice on its first voyage.