Last year I started having an issue where I could not get power and RPMs unnder load. Engine revived correctly sitting idle but not in drive. Took it in had it serviced they found a bad head gasket and some other issues got it fixed up and then it was not much better year ended fast for me this year I am getting it ready and again no power with just myself and one other in boat could barely get 3100 RPMs used to run 4000 to 4100 and could travel at spees of aprox 20 to 22 MPH via a gps.. I could only run 8 to 9 MPH at the 3100 RPMs and it really feels week. I dont need to be a speed demon I just want it to at least perform as good as it used to.

BTW it is a 2011 23HP vangaurd surfice drive motor.

Thanks for all help and suggestions in advance.

Sure both cylinders are firing?

Check for intake manifold leak at head. May of had a gasket failure.

Stuck valve taking out a cam lobe?

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