View Full Version : Generous GPS???
MR MAGOO
10-02-2002, 07:30 PM
I had stumbled across the thread by 22ZX about GPS speeds that were thought unheard of. I have a 22 Sea Ray Pachanga with a 350 Magnum. The boat goes pretty well for a stock small block 22' boat. Today, I was playing around with props and I am running a 13.25x23 Vengence at 4950 rpm.
My GPS reads 64.0 mph
Can a gps read high?
HyperDonzi
10-02-2002, 07:37 PM
Never. A GPS will only read slow wink :D
blackhawk
10-02-2002, 07:44 PM
I think the max speed function can be generous at times.
Rootsy
10-02-2002, 08:59 PM
when i run with my GPS i have it on actual speed... the GPS being in front of me, mounted on the railing, i can see the speed change as i run trimming to achieve optimal... the max speed on my GPS 99% of the time turns out to be the fastest speed i saw while watching instantaneous speed... my gps seems to be within a few tenths of an identical model (garmin etrex) which is one year older...
what i have found though... when my gps aquires satelites it gives me an accuracy of so many feet for various reasons (clouds, weather, worldly location etc) this can be 5 feet or 300 feet. the smaller the footage the more consistant and accurate it tends to be. I have compared my gps to both of my vehicles speedometers as well as one with a digital speedo readout and a few other various vehicles i have happened to be in with it and it can vary up to 2 mph if it gets 100+ feet in accuracy, the greater the footage of accuracy the more deviation i see. if i can get under 30 feet in accuracy it will generally be within +/- a few tenths.
anyone else done any investigation such as this?
Shanghied Again
10-02-2002, 09:09 PM
Are you sure about your prop size? Pachanga usally run a 14.25 and run at 61mph. Sea Rays are heavy but they run great!
BigGrizzly
10-02-2002, 09:09 PM
I have and came up with the same as you. My brother is a nave freek and has all the good stuff we are never more than 35 feet away from the point.
I've seen some funny numbers with my max speed on the gps. I never feel comfortable with the Max speed until I can duplicate it a few times in a row or shoot it with the gun.
RedDog
10-02-2002, 09:56 PM
Geoo - ther is nothing funny about the numbers in your avatar - even if they were off 10% they are scary to me!
MR MAGOO
10-03-2002, 05:38 AM
Frank, I have run MANY different props on the Pachanga and it runs the best with the 23 Vengence. I was told it is a 13.25 dia. but did not check it myself. I did put it hub to bub with the 21 Mirage that I had previously and it was smaler in dia.
I had done testing the same as Jamie had suggested.
Rootsy
10-03-2002, 08:08 AM
is the P/N for your vengence 48-16320A45 ? if so then it is the 13 1/2 x 23. the 21 mirage is 14 3/4 inches in diameter.
Bryan Tuvell 33ZX
10-03-2002, 08:11 AM
In the better GPS's there is a function that allows you to turn on/off the speed filter.
I have that function on my 176 and always leave it on, I will reread that portion tonight.
FYI
Bryan
Ranman
10-03-2002, 09:41 AM
I've had my Garmin III Plus give erratic MAX SPEED readings in the past. One time it told me I hit 84 MPH. This is an obvious error. It only happens once and a while, and I like the statement about duplicating your speed with multiple readings. I've been able to duplicate 66-68 in my boat many many times.
Jamesbon
10-03-2002, 10:04 AM
FYI
No matter how many times I use my GPS, the max. speed is always stored in the memory, that is, until it's manually reset to ZERO!
I saw 85 max speed in my Rabco...after thinking for a minute, I realized I had used the GPS in the Durango the day before...DAMN!
MR MAGOO
10-03-2002, 05:03 PM
My neighbor had shown me his new GPS, as I was checking it out the max speed read 648 mph. eek!
He had it on while in an airplane :D
Shanghied Again
10-03-2002, 08:37 PM
Hey we had a top speed of 112 out of my 26 3 weeks ago at an idle, Talk about a thrill ride!
boldts
10-03-2002, 11:31 PM
I got a 83.4 while testing a Hydromotive 4 blade. I'm thinking "I got to buy this prop!" Then I ran it again after reseting the GPS to 0 as I had done before it said 83. This time, the expected 65. Great ruff water prop though.... :D
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