Reply With QuoteKojac,
I have zero experience, but have heard only good things about GPS speedometers. The Rex website has a pic of the below deck antenna but not of the above deck model. I assume it is similar if not exactly this one.
I called Rex Marine today about purchasing a GPS to install in a 19ft stealth tunnel jet. I am a little vague about where to mount it and how accurate they are compared to a Decauter radar gun. Jay said there are two types. One has a reciever that mounts below the deck about the size of a computer mouse and the other mounts above the deck the size of a quarter.
I would prefer to replace the gaffrig speedometer presently in the dash and would like to avoid cutting unnecessary holes in my ride. I would appreciate any comments from fellow jetboaters that have experience with gps"s regarding installation and reliability.
Thanks Dale.
Kojac,
I have zero experience, but have heard only good things about GPS speedometers. The Rex website has a pic of the below deck antenna but not of the above deck model. I assume it is similar if not exactly this one.
They are similar to that picture, but are larger than a quarter and white in color. I will try to get a picture up on the website soon. As far as receiver location and what works it seems to vary widely between boats. Some work fine when mounted under deck, some don't. We actually recommend that you temp wire the reciever so you can move it around and find the best reception the first time (on the Garmin mouse style).
As far as accuracy, I know of no other speedometer that's more accurate than GPS.
As a side note you can also wire the AutoMeter GPS speedo into a Garmin hand held GPS (with the addition of a little wire loom). So for a guy who already has a Garmin hand held (I forget which models are applicable), you can save the cost of the receiver which substantially reduces the cost of adding the GPS speedo (by roughly half). You still have to mount the handheld somewhere though. We will probably make some billet dash brackets for them but haven't done so yet. Using the handheld as your reciever also gives you the other GPS functions available too (an added plus if you have the need for coordinates, etc.)
If you have further questions let me know and I'll get you the answers.
Thanks for the quick replys. Budwieser I appreciate the picture. It makes it clear what I have to do to create a mounting bracket for the receiver.
Mike I have two questions that you might be able to answer.
1.What is the accuracy compared to the radar gun.
2.I forgot to ask Jay if the gps was digital or analog.
I'll call tomorrow and order one.
Thanks,
dale..
kojac:
Thanks for the quick replys. Budwieser I appreciate the picture. It makes it clear what I have to do to create a mounting bracket for the receiver.
Mike I have two questions that you might be able to answer.
1.What is the accuracy compared to the radar gun.
2.I forgot to ask Jay if the gps was digital or analog.
I'll call tomorrow and order one.
Thanks,
dale.. Dale on your first question for a technical answer, I don't know. Not all that familiar with radar guns accuracy or calibration requirements. I do know that GPS is about as dead nuts as you can get though (taking this from what I've heard from those who build them and those who've used them for awhile). If you want tech data on the GPS as far as accuracy let me know and I'll dig it up. From my experience though over the years I'd think while GPS likely has an edge in accuracy over radar it's probably negligible for all practical purposes if both units are operating correctly.
The Auto Meter GPS's are all analog. Digital can be very hard to read in sunlight at certain angles. We've experienced this in the past with others like the Nordskog as well as digital gauges.
The issue with GPS is that it is not as quick to update as radar. Radar pulses many times per second while GPS calculates 1 or 2 times per second. This is not a big deal unless you are looking for accurate speed at certain times/distances.
cruser
If the sending unit only updates 1-2 times per second this likely would not be very accurate in a rapidly accelerating boat. The read out would always be lagging behind the actual speed. Are there some units that update at a higher rate?
the difference between gps and radar is you can see your speed in the boat with a gps and a radar you can't.
How much $ does the whole gps speedo set-up cost.
We have used both for some time for testing race boats. We find that the GPS is a vey accurate speedometer for reading your speed while cruising, but it very seldom reads the same as the clockes at the races, the radar gun, or the Nordskog Tell Tail test speedometer on top speed. The GPS will read the top speed accurately though if you can hold it at that speed for a few seconds. A lot of times that's just not possible when running over 100 mph. (in other words, Great for a 80 mph lake boat). This has been just our personal experience. Duane HTP
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