I have a 1648 G3 with a 40hp force with tilt and trim. The prop has an 18" pitch. I installed a tach and im not sure if its adjusted right to show the accurate RPMs. Is there any way i can find out about what RPMs it should be running at WOT to check it with my tach or is there any way i tell if the tach is giving the correct reading. Thankds alot for your help