Speedo not working; how to test fix?

Gunn

Gunn

Well-Known Member
TECHNICAL Contributor
Oct 4, 2006
2,335
Potomac River - MD
Boat Info
2003 280DA and 1995 Sea Ray 175
Engines
Twin 4.3l and 3.0l, all w/ AlphaI GenII drives
Late last season my speedometer abruptly quit working. I figured I clogged the tube or something. Well, I noticed that the little 1/4" or so black tubing near the outdrive looked to be nearly pinched in half. I cut the tube and added one of those 1/4" splice's, like those used for miniature drip irrigation. Fit perfectly. When we went out again, it still didn't work.

This weekend I plan on getting the boat ready for the season (I know, I know, I'm way late!). I want to fix this. Is there any way I can test my fix in the garage? Not sure if just blowing into it will register, or if anything special has to be done. From what I think I know, it uses a pressure differential to register a speed...(?). I'd rather test it there so I can get it fixed, without having to spend a lot of time taking it in and out of the water.

Thanks,

Tom
 
If you have compressed air handy, blow it over the hole in the pick up, not directly into it.
 
Have your wife do it.

EDIT: (So you can observe the gauge).
 
The pickup is in the leading edge (forward) of the drive, slightly above the gear housing. You'll see a very small hole. That goes hole goes in an inch and half or so, then makes a turn to go up towards the fitting you've already seen. 99% of the time, what has happened is debris has gotten lodged in that hole.

Take a small drill bit and BY HAND, twist the drill bit back and forth to remove debris. Eventually you should get the bit all the way in. You'll be able to feel when you get all the way in. Don't worry, you won't be hitting anything rubber.

Yes, you can test it out of the water. You can use a compressor, keep it low on the psi, though. If someone seals their lips well enough against the hole, they will be able to blow in there well enough to move the speedo needle a bit - I believe this is where the wife comes in handy...
 
Lazy Daze said:
If someone seals their lips well enough against the hole, they will be able to blow in there well enough to move the speedo needle a bit - I believe this is where the wife comes in handy...
Click to expand...

Maybe I should have said girlfriend?

EDIT: Or, wife's girlfriend? : )
 
Great tips guys. My wife won't have any problem with that task at all; it's just convincing her to do it that may take awhile. Maybe I'll do some laundry tonight. :grin:
 
Lazy Daze said:
The pickup is in the leading edge (forward) of the drive, slightly above the gear housing. You'll see a very small hole. That goes hole goes in an inch and half or so, then makes a turn to go up towards the fitting you've already seen. 99% of the time, what has happened is debris has gotten lodged in that hole.

Take a small drill bit and BY HAND, twist the drill bit back and forth to remove debris. Eventually you should get the bit all the way in. You'll be able to feel when you get all the way in. Don't worry, you won't be hitting anything rubber.

Yes, you can test it out of the water. You can use a compressor, keep it low on the psi, though. If someone seals their lips well enough against the hole, they will be able to blow in there well enough to move the speedo needle a bit - I believe this is where the wife comes in handy...
Click to expand...

Thanks! I have the same problem and started looking around for a paddle wheel or a sensor mounted on the transom. I'm used to larger boats. I had no idea the speed sensor is a pitot tube like device on the outdrive itself.
 
David Morgan said:
Thanks! I have the same problem and started looking around for a paddle wheel or a sensor mounted on the transom. I'm used to larger boats. I had no idea the speed sensor is a pitot tube like device on the outdrive itself.
Click to expand...

No problem! One could own an outdrive for years and never know that hole is there - it's very small.
 
Lazy Daze said:
The pickup is in the leading edge (forward) of the drive, slightly above the gear housing. You'll see a very small hole. That goes hole goes in an inch and half or so, then makes a turn to go up towards the fitting you've already seen. 99% of the time, what has happened is debris has gotten lodged in that hole.

Take a small drill bit and BY HAND, twist the drill bit back and forth to remove debris. Eventually you should get the bit all the way in. You'll be able to feel when you get all the way in. Don't worry, you won't be hitting anything rubber.

Yes, you can test it out of the water. You can use a compressor, keep it low on the psi, though. If someone seals their lips well enough against the hole, they will be able to blow in there well enough to move the speedo needle a bit - I believe this is where the wife comes in handy...
Click to expand...

old post but I just purchased a 2005 300sd and my analog or digital mph gauge is not reading. I have a sensor in the back of the stern motor with a tube looks to be like a pilot hose. could that be removed and force air through that or is there no clamp that holds the hose down below. my boat is in the water
 
I'm not sure what you're asking about with your second to last sentence, but from the pitot sensor, backwards toward the drive, it is essentially just one, long tube
 
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