Yamaha 90hp outboard

Question
The speed/mile p/hour indicator on the instruments panel of my boat has suddenly stopped working. At times it only shows a dash, and when it does show the speed, it changes slowly and is incorrect. What can be causing this? How does the instrument pick up the speed of the boat in the water?

Answer
Your speed sensor is on the bottom of your hull.  Look for a paddle or a tub on the bottom that may have dirt in it.  You can use some a vinegar or other acid cleaner to dissolve any organic mater keeping it from working well.  A tooth brush can help, and rinse well with a hose.

Best of luck.

Harvey Chichester
Coast Guard Auxiliary