pitot tube speedometer

[Commodore]

I have a Regency pontoon with a Mercury 250 outboard. The speedometer that runs off a pitot tube does not work until I get to 24 MPH, then it reads normal at any speed until I stop. Then I have to get it back up to 24mph again before it works. I have a GPS for speed, but the fuel consumption per mile needs the pitot tube reading to do the math, so I would like to have it working. Any ideas?

 

[PontoonaMatata]

Had a similar issue before, turned out my pitot tube was partly clogged. I'd check that first, then blow out the line with some compressed air. Also worth making sure the tube's aligned right. Have you tried clearing it yet?

 

[Commodore]

Haven't tried anything yet, but I'll try those ideas. Thanks.

 

[Commodore]

My pitot opening on the outboard is clear, but I don't see any tube exiting the outboard or going into the back of the speedometer, only wires. I looked for a paddle wheel, but see none anywhere. Strange setup. I wonder if the pitot is changed to an electrical signal some where before reachiing the back of the speedometer, because there are only wires going in.

 

[Commodore]

I found out that the transducer that converts water pressure to electrical signal is on the motor, so no hose to the speedometer.
I also found out that my GPS unit is compatible with the speedometer and that the GPS speed signal can be sent to the speedometer, which is even better than fixing the pitot system.

 

[floatlifecrew25]

That's a great discovery! Using a GPS feed for the speedometer tends to be more accurate and saves the hassle of maintaining the pitot system.