G'day<br />I've a 1973 evinrude 50hp that refuses to rev. It runs as smooth as silk up to about 2500 revs at 10 knots on a 16ft half cab fibreglass boat. But at full throttle it coughs and actually runs slower than at three quarter throttle. It chews the juice up at about 20 litres (5 gallons U.S.?) per hour. No suspect noises and good compression. Any suggestions fella's.