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Speed odometer justvstarted acting up!

T

Twopak

New member
My speed odomoter just started acting up, at first is does not work at all but when I get on plane it starts working but is way off, say's going 30 at idle then once I am running full Throtle is says 30 to 40 when I am running about 53. Any suggestions?
 
What boat? What engine?

Most marine speedometers are operated by a pitot sensor mounted on the transom so that the tip of it is in the water stream, facing into the oncoming water. On some engines the opening for the pitot tube is on the leading edge of the lower unit. You will see a small hole there. From the pitot sensor will run a small tube all the way to your speedometer. The speedometer itself is just a pressure sensor reading the water pressure in that pitot tube.

First, find the opening for the pitot sensor and gently clean it out. Be careful not to damage the little diaphragm in there. Check the tube all the way to the speedometer for breaks or kinks. Carefully check where the pitot tube connects to the speedometer. Then check the speedometer itself for good electrical connections from the key switch and to ground.

I got so frustrated with the internal pitot pickup on my Honda 225 getting clogged, that I cut and plugged the line where it comes out of the engine, then installed an external pitot on my transom. I think they cost around $25.00 from West Marine. The external has less of a chance of getting clogged and if it does, it can be easily cleaned out and low pressure air reversed through it. If that doesn't work, I simply install a new one.

Having said all of that, these things are not very accurate, especially at low speed. So you are better off relying on your GPS for an accurate speed reading.
 
chawk_man said:
What boat? What engine?

Most marine speedometers are operated by a pitot sensor mounted on the transom so that the tip of it is in the water stream, facing into the oncoming water. On some engines the opening for the pitot tube is on the leading edge of the lower unit. You will see a small hole there. From the pitot sensor will run a small tube all the way to your speedometer. The speedometer itself is just a pressure sensor reading the water pressure in that pitot tube.

First, find the opening for the pitot sensor and gently clean it out. Be careful not to damage the little diaphragm in there. Check the tube all the way to the speedometer for breaks or kinks. Carefully check where the pitot tube connects to the speedometer. Then check the speedometer itself for good electrical connections from the key switch and to ground.

I got so frustrated with the internal pitot pickup on my Honda 225 getting clogged, that I cut and plugged the line where it comes out of the engine, then installed an external pitot on my transom. I think they cost around $25.00 from West Marine. The external has less of a chance of getting clogged and if it does, it can be easily cleaned out and low pressure air reversed through it. If that doesn't work, I simply install a new one.

Having said all of that, these things are not very accurate, especially at low speed. So you are better off relying on your GPS for an accurate speed reading.
Click to expand...

It is on a 2008 Glasstron DX 235 Volvo Penta 5.0 GXI-J Inboard/Outboard! Dual Stainless Prop!
 
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