Ever tried adjusting speedometer?

[youmansjason]

I was comparing the speedometer on my handheld GPS vs. my old pitot style boat speedometer today, and the boat speedometer is a good 5 MPH off (on the low side). I've recently replaced the pitot and tubing thinking it was blocked or something, but that didn't help.<br /><br />Has anyone ever tried adjusting the hole on the pitot tube? Wouldn't a larger hole create more pressure in the line and therefore give a higher speed rating? I know it would be very trial and error, but I just like to see the boat speedometer read a bit more accurate.

 

[xltier]

Re: Ever tried adjusting speedometer?

i may be wrong but i think the pressure in the line is determined by the speed of the boat,not by the size of the hole.

 

[sangerwaker]

Re: Ever tried adjusting speedometer?

Won't help, unfortunately. Speedos are very seldom accurate, unless they are able to be calibrated, like some tournament style ski boats. <br /><br />We tested a boat today, and the speedos were alomost 8 MPH off. This was a tournament style inboard! It just didn't have the calibratable speedometers. (they were digital actually)

 

[Mark42]

Re: Ever tried adjusting speedometer?

What brand speedo? Some, like the Teleflex line list what the speed reading is for various pressures. So it is easy to determine if the speedo is off by directly connecting to pressure source or if the line/pickup is the problem. I have Teleflex info that says their standard speedo can be off after sitting for a while because of the buildup of some corrosion on the internal moving parts that will go away with use. Has your speedo been sitting unused for a while?

 

[bomar76]

Re: Ever tried adjusting speedometer?

Easy to fix...<br /><br />1. Carefully place black electrical tape over entire face of speedometer<br />2. Buy a cheap handheld GPS unit and use it.<br /><br />Bingo!<br /><br />Accurate speed readings!<br /><br />Boat speedometers (the pitot type at least) are wildly inaacurate.

 

[wvit100]

Re: Ever tried adjusting speedometer?

The speedometer on a boat is about like tits on a hog. The boat will only go as fast as it goes and you don't see many speed limit signs on the lake. I know my top speed is about 60 to 65 mph and it cruises at about 30 mph. My pitot has been plugged for over two years now and you get used to not having one. I used to worry about it when it didn't work and would clean the pick-up every couple of weeks. But after you get used to not having a speedometer you don't really miss it.

 

[bomar76]

Re: Ever tried adjusting speedometer?

There are quite a few places in central Ohio with speed limits of 45 MPH.....and they do cite people for breaking it.

 

[Mark42]

Re: Ever tried adjusting speedometer?

Originally posted by wvit100:<br /> .... I used to worry about it when it didn't work and would clean the pick-up every couple of weeks.

So you're saying that the reason you're speedo doesn't work is because of local boating conditions clogging up your pilot, not because the speedo broke. I bet that is the problem with most folks who complain about problematic speedos.