Okay the two really have nothing to do with each other. The speedometer uses a pitot tube with a tube attached to the back of the speedometer. And how it actually works is the water pressure is transferred to the gauge and read as speed. Your gauge probably doesn't have equal spacing to show speed. And that's because the pressure isn't linear but logarithmic. So if it isn't working, check for either a plugged pitot tube on the engine itself, or a pitot tube attached to the transom with a tube attached. Here is a picture of a standard transom mounted pitot tube;
You can see how the tube is attached in this picture.
Now for the tachometer. There are a few things that can keep a tach from reading. The tach isn't connected up correctly, or the tach is bad, or the stator on the engine is defective. So you have to see if the tach has the correct connections first. There should be a positive wire and a ground wire going to the back of the gauge. Make sure the positive wire has 12 volts on it, and you have a good ground as well. Then there should be a third wire that goes to the engine and depending on the engine where that wire would be connected. If a basic 2 cycle outboard, then that wire attaches to the stator output... So make those checks and post back here with your results... :thumb:
