In 1978, Johnston introduced the first single furnace waterback 4-pass Scotch Marine boiler. Water backed reliability with 4-pass design efficiency? A dream come true.​

​​Every Johnston 4-pass maximizes effective heat transfer using a full five square feet of heating surface per BHP, while at the same time eliminating tube sheet stresses and costly maintenance repairs that are common with dry backed designs.

Today, the Johnston 3-pass boiler is still a strong and dominate force in the boiler industry with its high steam and water storage areas, high efficiencies, rugged construction, and its ability to keep up with wide load demands.

Many boiler users over the years have seen the benefits of using a Johnston boiler. Low maintenance costs, high reliability, high performance, and lower fuel costs have paid back their initial investment many times over.

4-Pass Boilers (50-1600 HP)

3-Pass Boilers (1800-2500 HP)