I recently purchased a 2004 Monterey 265 with a Volvo Penta 5.7 GXI-F - 500 hours. This was the first tank of ethenol fuel to be run through the boat @ 86 octane.
Second trip out I could not get over 3000 RPM/ 15 mph and motor was popping. Heard a whining or squeal that I thought was an idler...
