I tokk my GPS on my 250 today and discovered my speedo read 7-8 mph lower than the actual (GPS) speed. Is there any way to have this corrected. I realize boat and jet ski speedos are not always acurate but this seems kinda extreme.

 

Even street calibrations are allowed to be 10% off under warranty for anomalies and tire wear. If you figure that is +/- 5MPH at 55.
So considering that the speed you see is from a paddle wheel that runs off water flowing by it turnig it allowing a magnetic sensor to read the number of times the little magnets are whizing by the sensor, that's not too bad.
All watercraft are off, boat or otherwise that use this system. Most people think that their ski's run 75-85 mph when in reality the fastest allowable manufactured speed it 65MPH by the US coast guard. That just goes to show you how far off they read and how people take what they read for face value. You have the fastest and quickestproduction boat built, be happy.

 

I totally understand they are not going to be very acurate. But mine won't even begin to register any speed (it just sits at 0) till I'm at about 2000 rpm and pushing a good wake.