Last summer my perfect pass started not holding speed. It will fluctuate 2-miles an hour.

I have an 2006 Supra 24SSV I replaced the PP about 3 years ago to a GPS model.

When I had the boat de-winterized I asked them to take a look at it and this was there response;

Check perfect pass for function
Description:check perfect pass for correct operation
Resolution: Pick up from storage, Water test for perfect pass, it does have a variation at slower speeds, this system works better at 18 miles per hour plus -- That is what boat is designed for. haul out and take back to storage

It didn't use to do this, why is it all of a sudden fluctuating now, and is this an acceptable response or should I push back?

Plus they charged me $220 to look at it which I'm on the fence about paying if it is something they should be able to fix.

I appreciate any educated assistance........Thanks