Speedo and pitot tube accuracy.

[tractoman]

Is there a way to make the speedo and pitot tube system consistent on an alpha gen II? I know it is not that important but would sure be nice if it were somewhat accurate.

 

[tpenfield]

Re: Speedo and pitot tube accuracy.

You will probably find that it is fairly accurate in the mid-range of speeds . . . like 25 - 35 mph +/-, if you compare them to a GPS. My boat is within an mph or 2 in that range, as was the case on my previous boat.

I have found that they barely read anything until you get up to about 20 mph and at higher speeds the pitot speedometers, read higher that actual. Not much you can do about it. Since many/most boaters have some sort of GPS . . . or even a speed "App" on a smartphone, there is not much concern about making the legacy speedo's any better.

 

[haulnazz15]

Re: Speedo and pitot tube accuracy.

It's likely pretty consistent. Accurate is another question. You'd need to take a GPS and record the variance from GPS speed at 5 MPH intervals to see how far off it actually is. If you don't have a consistent variance across all speeds, then I doubt there is a way to correct it. The other question I'd pose is: Who Cares? What are you doing that you need perfectly accurate speeds? Unless you are towing for watersports tournaments, or trying for offshore racing, how does the speedo accuracy affect you?

 

[Scott Danforth]

Re: Speedo and pitot tube accuracy.

if you want an accurate speedometer, get a GPS unit. The pitot tube speedometer is telling you an estimated speed based on water pressure. direction of current, debris, and water density all effect the reading. if your going up-stream or down stream your reading will change. there is no easy/cheap method of even getting it to be consistent, much less accurate. It is merely a suggestion of speed.

FYI - the OEM's pay about $20 for most pitot tube speedometers and tachs, and about $5 each for the remainder of the gauges. A little more for the pretty gauges. (and yes, to the average consumer, there is about 10x markup)

 

[tractoman]

Re: Speedo and pitot tube accuracy.

I don't do anything that makes it critical. I just like to have stuff work properly. I have a gps and speedo app on my phone too. On my boat it just seems very inconsistent and I would like to have a better idea of what speed I am going at different rpm's and I can see the speedo much better than the phone out in the sun and the gps is a little clumsy while I am driving.

 

[ewpvic]

Re: Speedo and pitot tube accuracy.

Luckily, mine is almost EXACTLY 5 mph slow according to GPS.

 

[JimS123]

Re: Speedo and pitot tube accuracy.

The only time I need to know exact speed is when I set the kicker for trolling. The best speed for my area and species is 1.9 mph. A GPS is totally worthless. My river current is about 1.6 mph, but even that changes with the wind and water depth. So downstream the GPS reads 3.5 and when I turn around it reads 0.3. I need to know the speed in relation to the water, not the earth.

A pitot reads spot on with the GPS in no current or wind - in the 10-30 mph range. The best device if you really want to know is a paddle wheel sensor that many depth finders are equipped with. Mine is spot on with the GPS at all speeds, in no current or wind conditions.