Fishermen's News - The Advocate for the Commercial Fisherman

By Einar Ask 

A History of the MARCO Puretic Power Block


February 1, 2020

The advent of the Power Block has revolutionized commercial fishing worldwide. Photo by Einar Ask.

The history of the Puretic Power Block is the history of all seine fisheries and seine systems since 1955. In just a few years, the Puretic Power Block changed seining methods around the world.

Mario Puretic

Like many in Europe at the time, Mario Puretic left his home on the island of Brac, in Croatia in 1938 to find a better life in the United States. He found himself working on tuna and sardine seiners in California and recognized there had to be a better way to haul those nets in. At the time seines were hauled over the rail by hand, and required several men to haul the net in, largely by grabbing meshes in each hand and pulling. Besides the wear and tear on the fishermen, the pulling would result in tears that needed time consuming mending.

The constant repairs, the hard work, the dangers, and the man hours to make and haul back just one set, inspired his invention.

Mr. Puretic envisioned a block hanging above from a boom that the net would pass through. The block would be powered from below and the net would be pulled through. In 1954 he developed a prototype and it tested well in trials, but there was little interest.

First Patent

In his patent, US2733530A, applied for on August 16, 1954 and issued February 7, 1956, the POWER BLOCK UNIT is described specifically for roundhaul purse seines, and the method of power was described as a mechanical linkage from a gasoline engine below. The block was V-shaped, rubber coated and free swinging, suspended from a boom. The Power Block was capable of more seining applications, and adding a more versatile power source was a missing piece.

Peter Schmidt and MARCO

Mr. Puretic brought his invention to Seattle in 1955 and installed it on the Seiner New Sunrise and demonstrated hauling a seine net at Seattle's Fishermen's Terminal. He met with Peter Schmidt, president and founder of Marine Construction and Design (MARCO). Mr. Schmidt and his engineer Don McVitte worked to refine, manufacture and market the new Puretic Power Block, and the improvements and versatility made the Power Block highly desirable in the salmon and herring fleets in Washington State, British Columbia and Alaska.

Adding hydraulic fluid power increased the ease of control of the block and its flexibility, as it could be swung from port to starboard and raised or lowered as needed by moving the boom.

Product Launch – salmon and Herring

The Power Block was introduced by MARCO to such great acceptance that they quickly outsold their manufacturing capacity in the first year. Before the Power Block it took hours to haul back a seine, and with a Power Block boats could make a complete set in under an hour. And boats only required half of the crew they once carried. It is easy to imagine fishing next to the first Power Block equipped boat in your favorite spot, only to see that boat making set after set while you struggle with traditional methods. It changed everything.

At MARCO it became clear that this Power Block was the key element of a complete seining system. They began designing more deck machinery that would work with the Power Block in vessels of all sizes. There were new deck winches and specialty winches for moving the boom, choking, and brailing.


In 1955 Peter Schmidt and MARCO were invited to make a presentation of their new seining system at "The Gulf and Caribbean Conference." The Menhaden seine fishery involved two small purse boats and a mother ship. The small boats handled the large nets, and all of the work was done by hand, with large crews on each of the small, open boats. The MARCO team showed films of the new Power Block in action, and the fleet managers realized this could change their fishery.

In December of 1955, the first Menhaden experiment was made with two open sided, rubber coated Power Blocks, one crudely mounted to davits in each boat. There was still a lot to be done and systems to be designed, but it was clear that there was potential. A method of hanging the Power Block on the small boats was critical and Mr. Puretic was involved in developing a crane with a pantographic design that allowed the Power Block to remain level while being maneuvered around the boat.

They continued experiments and research from 1956 through 1958. This included Menhaden skippers coming to the Pacific Northwest to see the Power Block and winches in action. New methods of pursing were developed for the fishery, including using removable purse rings in part of the net.

California Tuna

The salmon and herring fisheries in the Pacific Northwest were changed, and by the late 1950s the struggling California bait boat fleet was now able to use a MARCO purse seining system to change over from pole and hook fishing to running synthetic tuna nets. In less than three years most of the tuna bait boat fleet in California had switched to seining.

Now that Marco was designing a system-wide approach to the tuna seine fishery, new, larger pieces of equipment were being developed such as larger deck winches, power units to drive the hydraulics which included up to 25 auxiliary winches and other hydraulic equipment on board. They developed and marketed an entire tuna seining package, which was the first of its kind and became the tuna seining industry standard.

Europe and South America

In the 1960s MARCO systems became popular in Norway, Iceland, Spain and Portugal. As the fleets shifted to MARCO equipment, manufacturing agreements were made with RAPP-Fabriker in Norway, and Tecnicas Hidraulicus of Spain. MARCO also developed special Power Blocks for the South African fleet.

In the 1960s Peter Schmidt and MARCO licensed vessel construction to Fabrimet Shipyard in Peru, then MARCO CHILENA in Chile, and then in 1964 MARCO PERUANA was formed. So, besides building ships and deck machinery in Seattle they could build ships and complete fishing systems at multiple locations in the world. And those complete systems included deck and auxiliary winches, Capsul pumps for pumping smaller species of fish, hydraulic pump drives, and of course a wide range of Puretic Power Blocks, from 19 inches to 90 inches.

The Puretic MARCO Power Block Today

Since the early days of the simple Puretic Power Block, many little changes have been made to accommodate the various fisheries and methods throughout the world. Here on the Pacific Coast the Marco Power Block ranges from the open sided B19 to the B33.

Powerblocks are used for retrieving welding leads and umbilical hoses in the diving and salvage industries, for the handling of large cables & lines for deepwater construction and for control and movement of shore power lines for the Navy.

Known for its reliable versatility and strength the 28-inch Utility Power Block was chosen by NASA for use on their at sea retrieval missions of the Space Shuttle's solid rocket boosters.


The first Puretic Power Block had a rubber coating and small ribs to grip the net as it hauled. The ribs were later molded into each sheave, and then removable cleats were introduced so that as the cleats wore down over use they could be replaced without replacing the entire sheave. The larger Powerblocks have the option of bolt-in rubber, aluminum, high profile polyurethane, and low profile polyurethane cleats.

Bolt-in rubber cleats offer the most gripping action. Bolt-in aluminum cleats are hard wearing and durable for a long life. Bolt-in polyurethane combine the durability of the Aluminum with a bit more grip. It's interesting to walk the docks and see how some boats mix and match their cleats to work best with their own net construction.

Power Grip

An early addition to the Puretic Power Block was the Power Grip. MARCO Power Grips are available as an addition to most models of MARCO Powerblocks and have been retrofitted on a number of different brands and sizes of Powerblocks.

The yoke mounted Power Grip helps keep the net square when hauling, increasing traction and control of the net in rough weather.

A swivel allows the Power Block to rotate 360 degrees. The load bearing hydraulic swivel option allows the Power Block to easily haul port or starboard without binding the hydraulic hoses.


Used with a Powergrip, the MARCO Swivel-Tilt improves hauling traction, and allows complete control over the incline of the Powerblock enabling the net to be hauled faster and more square from either the port or starboard side. The Swivel-Tilt is used with the Hydraulic Swivel that allows 360 degree rotation of the Powerblock enabling it to easily follow the load.

Another popular upgrade to existing Power Blocks is adding a two speed motor. This gives the skipper the option of hauling that lighter part of the net in quickly, and then getting more pulling power when needed.

Smith Berger Marine, Inc + MARCO

Smith Berger Marine, Inc. purchased the assets of MARCO in April 2017, but the MARCO products, including Powerblocks, pot haulers, deck winches and salmon processing equipment, continue to be manufactured and repaired at Smith Berger's South Seattle facility.

Einar Ask started trolling and longlining on the Fairweather Grounds in 1969 out of Pelican, Alaska with his father Ingvald Ask on the 48 foot Agile. He worked at Seattle Marine for 18 years in sales, advertising, catalog making, and eventually web design and ecommerce. He is a musician, writer and artist for pleasure and is currently freelancing for a living.


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