Here is a link to current regs and OSMB page.
OSMB Laws Index
Oregon State Marine Board web page
Multnomah Channel, Columbia/Multnomah, 250-020-0051, 250-020-0282
Slow-no wake, maximum 5 mph for motorboats:
-- within 200' of moorages between Hadley's Landing and Willamette River;
-- within 200' of the public transient moorage at Coon Island;
-- within 200' of the Gilbert River boat ramp;
-- on Scappoose Bay within 200' of Bayport Marina and public ramp.
David