engine lost power

Hi, I'm a new owner and new to the club :) Basically I'll start up fine (after pumping the throttle 2 times first), head out fine, open her up (WOT) and then when I want to come to a complete stop (shift immediately into neutral) the boat sounds like it gets bogged down and completely stalls...

At cruise speed, port engine suddenly lost the ability to fully rev and lost power. Sounds rough, and only revs to 3000. This is the second time this has happened. The first time the symptoms just disappeared after doing a compression check, replacing plugs, and installing new spin on fuel...