Speedometer

[joshstan1978]

I have a mercruiser Apha One Gen One that the speedometer quit working on. I don’t want to replace with a gps unit kinda just trying to learn about boats. There was a pinch in the line running between the speedometer and the plastic intake mounted on the transom. I fixed that and air blows from the tube by the speedometer and the plastic white pickup sensor (terminology??) on the transom. Still just stays at zero and doesn’t move. I have tried checking the out drive but I can not find the hole one mine. Is it because it’s a gen one??? It is not on the front edge of the out drive. I can not find a hose running up through the out drive like a gen two. What do I try next ?

 

[Scott Danforth]

pretty sure your gen 1 alpha may be before the pitot tube connection.

just spend $20 on a new plastic pitot pickup and tube and replace the line to the dash.

https://www.amazon.com/Speedometer-Universal-Automatic-Kick-up-Assembly/dp/B08F35XJRD?th=1

 

[joshstan1978]

That’s what I was wondering. Is there a way to test the speedometer to see if that’s the issue?

 

[Alumarine]

That’s what I was wondering. Is there a way to test the speedometer to see if that’s the issue?

You can run very low air pressure to it.
That won't tell you how well it works though.

 

[joshstan1978]

But it would tell me if the needle moves. Great idea. If it doesn’t move is that a sign something failed in the speedometer itself?

 

[Alumarine]

But it would tell me if the needle moves. Great idea. If it doesn’t move is that a sign something failed in the speedometer itself?

Yes.

 

[nola mike]

I fixed that and air blows from the tube by the speedometer and the plastic white pickup sensor (terminology??) on the transom.

Pitot.
Gen 1's have don't have a speedo in the drive. Should have a stand alone pitot on the transom. They're pretty fragile. Google an image.

 

[Scott Danforth]

get a small bit of hose. connect directly to the speedometer. you should be able to blow into the hose and get about 5-10 mph on a pitot tube speedometer.

couldnt post the pic of the speedo calibration, so I typed it.

If adjustable air pressure is available, standard calibration speedometers should react to the following pressures:
5 psi = 20 mph, 11 psi = 30 mph, 19 psi = 40 mph, 30 psi = 50 mph