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1999responselxlostlake

speedo's

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1999responselxlostlake

What is the best way to diagnose a speedometer problem? The left hand pick up works, but not my right. Does not appear to be any cracks in the tubes.

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kjstorch

I had a similar problem on my '98 Sunsetter. I found a place in the back next to the gas tank where both vacuum tubes went into these seperate cylinders. So, I swapped them at that point from Left to Right to confirm if it was an actual Speedo guage issue. In my case it turns out one of the pickups was bad. At the very end of the pickup, there was supposed to be a plug that I assumes fills a hole from the manufacturing process, but it had fallen out. So, I actually put some tape over the hole since I couldn't think of anything small enough to plug it with and it's worked ever since.

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wienrdog

The feeds from the rear of the boat should be separate for each speedo. Should go Pitot -> Black Tube -> Brass Tube -> Black Tube -> Speedo

Pickups could be either normal pitot or venturi type.

Normal type has hole on front & no hole on back.

Venturi types have little tube on bottom with narrower hole in the back.

1) Look for a blockage in the tube leading to left speedo - could be either pick-up. Unhook from behind speed & try to blow through it. If blocked, work your way back to pitot to find blockage.

2) Blow through the pickup (don't use a compressor) into the back of the gauge to see if the needle on the speedo moves (or switch tubes on back of speedos). Could be a broken gauge - the diaphragms inside can rupture.

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EchelonMike
What is the best way to diagnose a speedometer problem? The left hand pick up works, but not my right. Does not appear to be any cracks in the tubes.

Funny, I have the same issue (97 Echelon LX). The right speedo actually works, but barely registers speed. The left seems fine and I am going to set it via GPS next time out to get it accurate.

I turned the knob on the dial to see if that would help, but even all the way "open" still only showed maybe 20 MPH.

Pick-up is down in the proper position. Will check to see if it is clogged, or if there is another issue with the tube before checking the speedo itself. Great idea about switching pickups at the transom, will give that a try.

Good luck!

-- Mike

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footnlongline

That happens to me often when boating in fertile water. I pull th hose off and blow down thru the pitot. Always works for me.

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jcaksume
The feeds from the rear of the boat should be separate for each speedo. Should go Pitot -> Black Tube -> Brass Tube -> Black Tube -> Speedo

Pickups could be either normal pitot or venturi type.

Normal type has hole on front & no hole on back.

Venturi types have little tube on bottom with narrower hole in the back.

1) Look for a blockage in the tube leading to left speedo - could be either pick-up. Unhook from behind speed & try to blow through it. If blocked, work your way back to pitot to find blockage.

2) Blow through the pickup (don't use a compressor) into the back of the gauge to see if the needle on the speedo moves (or switch tubes on back of speedos). Could be a broken gauge - the diaphragms inside can rupture.

I am in the process of putting new speedo tubing on my boat since neither of the gauges have been working. I replaced the gauges last year. My question is....what is the purpose of that Brass tube. One guy I talked to said it converted the water pressure to air pressure that goes to the gauge. Was he correct? I also have a speedo de-clogger by my left knee when in the drivers seat. How does the declogger work? It has two separate buttons that you can depress. The box is about 1" thick and 8" x 10" approx.

Jamie

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wienrdog

The brass tubes are/were called 'pulsation dampeners'. At least that's what they were called when I bought one for my last boat.

There will be an air-water pressure conversion without using the brass tubes, but it can/will fluctuate more rapidly without them. Not sure how the tubes work, but my guess is they increase the diameter and volume of the transition area between air & water in the tube to make the speedos less bouncy in case of rough water or currents. They may also have a smaller opening somewhere in the middle of the tube.

Not sure about the de-clogger, but I've heard of people plumbing a blood pressure cuff bulb into the speedo lines to blow something back out.. Pump it until the clog goes away. I'd guess the declogger works about the same, but in a prettier package.

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