A different kind of speedo question

[vetplus40]

What does the speedo assembly (if any) look like inside the lower unit of an Alpha One drive? I have looked at a few exploded views and simply cannot tell. I am trying to find out what is between the notch in the leading edge of the foot and the quick disconnect atop the lower unit where the speedo tubing connects to. Is there simply an open cavity, or is there possibly a piece of stainless tubing inside the lower unit that connects the two? Also, if you were to take a small drill bit and clean debris out of the notch in the forward edge and accidentally drill too far, would you actually drill into the compartment where the gear lube is contained? Basically, I am just trying to get an idea of what's inside the lower unit that makes up the speedo assembly. Thanks.

 

[Bondo]

Is there simply an open cavity, or is there possibly a piece of stainless tubing inside the lower unit that connects the two? Also, if you were to take a small drill bit and clean debris out of the notch in the forward edge and accidentally drill too far, would you actually drill into the compartment where the gear lube is contained?

Ayuh,....... Yes,..... 'n Yes,......

 

[achris]

The speed pick-up 'tube' is just part of the casting, there's nothing 'in there'. And yes, drill too far = oily mess. But you'd have to be really pushing it to go that far. What's your pick-up in the drive (not 'foot') blocked with? (The old MC-1 and Alpha housings had a drain at the front of the drive that almost always clogs up with salt and produces of corrosion. I'd drill out the hole at the front slightly bigger, then use a long drill to clear out the vertical passage).....

Chris........

 

[Lowlysubaruguy]

Try googling pitot tube mercruiser Alfa one my tablet isn’t user friendly for moving links but theres a few diagrams that might show you what you need to know. Mines usually just plugged up I’ve hit a few submerged logs use a small drill bit by hand not on a drill then a bent paper clip will usually do what needs done.

Or is there something else that’s requiring you to go deeper?

 

[achris]

Removing the tube from the back of the speedo and blowing compressed air down also helps...

But my main question is why, in this day and age of free GPS apps on smartphones and cheap receivers in cars and boats, are people still using inaccurate pitot tube speedos? :noidea:

Chris..........

 

[vetplus40]

I had heard others that I boat with refer to the bottom part of the lower unit as the "foot",that is why I used that term which is apparently not correct. That said, I was finally able to clear the obstruction (likely a piece of wood) by putting soapy water in the speedo passage with a syringe and tubing and letting it soak overnight. I then blew it out with an air compressor.

I had looked at a few exploded view drawings and just couldn't tell exactly what I was looking at. I do thank you all for your insight and knowledge. I just wanted to have a better idea of what I was dealing with. Thanks again.

 

[achris]

I had heard others that I boat with refer to the bottom part of the lower unit as the "foot",that is why I used that term which is apparently not correct. That said, I was finally able to clear the obstruction (likely a piece of wood) by putting soapy water in the speedo passage with a syringe and tubing and letting it soak overnight. I then blew it out with an air compressor.

I had looked at a few exploded view drawings and just couldn't tell exactly what I was looking at. I do thank you all for your insight and knowledge. I just wanted to have a better idea of what I was dealing with. Thanks again.

:thumb: