80's Merc Speedometer

[andrewkafp]

Any Idea how they work ?

 

[Elmer Fudge]

Re: 80's Merc Speedometer

I think they're calibrated to function by water pressure.

 

[walleyehed]

Re: 80's Merc Speedometer

Combination of water and air.....water pushing (compressing) air inside the line between the pitot tube and gauge....the merc version was not known for accuracy.

 

[andrewkafp]

Re: 80's Merc Speedometer

So.. Water enters through a lttle V shaped hole in the front of the L/U and applies pressure to a device in there ?? That pushes water up the tube and to the back of the gauge ?<br />Mine has ceased to function.<br /><br />Close ??

 

[walleyehed]

Re: 80's Merc Speedometer

The water pressure compresses the AIR between pick-up, and gauge.....doesn't matter if it's built into the L/U, or a pitot tube mounted to the transom, the basics are the same....

 

[andrewkafp]

Re: 80's Merc Speedometer

Does that small hole supposed to have a bit of plastic tube wedged in it. Mine did have until I tried to unblock it. 1/2" bit of tube came out with the wire. But as least it's no longer blocked.

 

[rickdb1boat]

Re: 80's Merc Speedometer

I'd just put a pitot on the transom and forget the one on the motor.<br /><br />

<br /><br /> Pitot

 

[walleyehed]

Re: 80's Merc Speedometer

I agree with the transom mount. Seems like there is always something stuck in the L/U tube or the tube pulls in 2 .......

 

[andrewkafp]

Re: 80's Merc Speedometer

Don't quite understand the Pitot function, as the one on the leading edge of the L/U is pointing in the direction of the water and the Pitot seems to be pointed away. How would it create pressure ?<br />Rick...Are you suggesting that I can just remove the tube, extend it, and hook it up the the above device ? I suppose some calibration would be in order ?? Your advice is appreciated

 

[rickdb1boat]

Re: 80's Merc Speedometer

Unicorn,<br /><br />Yes, you would just hook up the tube to the pitot in the picture. What you don't see in the picture, is that there is a hole in front of the pitot that picks up pressure from the water as you move along. No need for adjustments after you install the pitot. It will work fine and more than likely, better. These pitots are designed to kick up if they hit something in the water. So if you lose your speed signal, that is most likely why. You just push it back down until it locks in and head off again. Also, they sometimes clog up if you boat in dirty water, Butn no big deal. You just clean it out and go. 99% of the time they are trouble free and you don't even think about it.

 

[andrewkafp]

Re: 80's Merc Speedometer

What'll they think of next ?? <br /><br />Thanx...