Controlling a SeaDoo's Speedometer.

I was wondering if someone can help me with an electronics problem. I want to control my SeaDoo's speedometer using an arduino and a gps. Currently the speedometer is controlled by a wheel on the back of the hull, that sends a pulse every 1/8th turn. If the Low pulse and high pulse were under 5vdc this would be no problem for me to make. Except.. Here is the problem, the pulse is low at 5.5vdc and high at 8.5vdc. I have no idea how to accomplish that, using an arduino. or if that is even feasible for this type of application. I really don't want to spend 150 for an aftermarket version of this when i have a couple of gps modules and mini pros laying around.

Will a voltage divider help?

If you cut the voltage in half, then your upper limit will be within the Arduino's maximum input range.

No sorry if i wasn't clear. I don't need to read the paddle in the back. I need to output a pulse that ranges between 5.5v and 8.5v. I want to eliminate the paddle and emulate it with a gps and arduino.

The SeaDoo's chassis voltage is? 8.5V?

It shouldn’t be since it runs on a 12v system. I don’t know why it uses 5.5v and 8.5v. I checked it with my multimeter, and it also says the same in the shop manual.

This is from the shop/service manual and i tried it
“Slowly rotate the paddle wheel. Every 1/8 turn, the observed voltage should fluctuate between 5.5 and 8.5 Vdc.”
The same pulse voltage goes directly into the speedo.

How much current does the speedometer need?

That is a good question i have not checked. Im sure it will be low. I have taken apart another speedo that was broken. They are waterproof so i had to dremel it open. Inside the speedo is a microcontroller that senses the pulse and controls the needle. The controller is a tb9226an. The pulse signal going into that controller goes through a voltage divider using 1k and 4.7k resistors.