200hp Vmax loss of power

[andybuck]

HI

first time to the forum and need some help
I have a Vmax 200 PETO which ran fine first time out after the winter. Second time out after about 20 mins, the power dropped away so much that the boat would not plane.
It would run ok at about 2000rpm and occasionally surge. I took it to the local yam dealer who couldnt find any problem after running the engine on a dyno. Some of the forum threads i have looked at seem to point to fuel - change the VST filter.
can anyone offer any ideas before the yam dealer asks me to remortgage my house?

[boats.net]

Not familiar with a PETO model, but run compression test, check for spark on all cylinders, check warning buzzer is working, have fuel pressure tested and computer diagnostic run on it if that model has data plug.