PORT TOWNSEND — The Steilacoom II, which is expected to begin service between Port Townsend and Keystone on Saturday, was tested for its ability to bear heavy loads on Thursday.

The Coast Guard has issued a certificate of inspection, certifying the car ferry as ready for service.

Steilacoom II sea trials on Thursday included a run in which four Fred Hill Materials dump trucks, two filled with gravel and two pulling trailers, were driven aboard the Steilacoom II.

The weight totaled 261,000 pounds.

The 50-car and 300-passenger Steilacoom II, which the state ferries system is leasing for $760,000 from Pierce County until April 2009, will replace the passenger-only ferry Snohomish on the route..

Steilacoom II sea trials in Port Townsend Bay and across Admiralty Inlet began on Monday.

State ferries system crews have trained over the past week to gain experience operating the vessel, familiarize themselves with the equipment and perform routine safety drills.

After testing the vessel in different weather conditions and practicing landings at the Port Townsend and Keystone terminals, the state ferries system determined that the vessel was ready for operation.