Mercury 115hp Outboard Speedometer Tube

[Skyboat]

I am doing winter maintenance on my 2016 Bayliner VR5 with 115 Mercury 115hp outboard. On my last cruise in November, I noticed that the speedometer was no longer working. I do have a Vesselview hooked up, but there are times when the screen on my phone is too glary and I like to just look at my analog speedo. I looked at some of the vids about cleaning the pitot tube, and mine was pretty clear. I was thinking that maybe after the pitot tube, where does the tube that runs to the back of speedo route? Does it come out of the lower unit somewhere? Is there a way to blow air back into the pitot tube to see if it is clear? Or is it better to remove the tube from the back of the speedometer and blow rearwards from there? Any help is most appreciated.

 

[Texasmark]

From memory, the pickup hole in the lower unit is on the leading edge of the casting below the height of the AV plate (has to be in the slipstream to have water to pick up) and is easily seen as is the tube carrying the inlet water. Attached to that is a hose and maybe a rt. angle fitting and the hose goes up a hole in the casting (all within about an inch or so) at right angles to the opening. It proceeds internally, vertically up to and out the right (Starboard) side of the wiring harness cutout on the top of the midsection along with the electrical control cable to the control box and depending on the installation, along with other accessory wires, zip tied to the side of the wiring harness. It has to continue to the rear of the speedometer unabaded since you are sending water pressure to the instrument. Its a black plastic hose about 1/4" in diameter.