Generous GPS???

[MR MAGOO]

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]

Never. A GPS will only read slow wink :D

[blackhawk]

I think the max speed function can be generous at times.

[Rootsy]

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]

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]

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.

[GEOO]

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]

Geoo - ther is nothing funny about the numbers in your avatar - even if they were off 10% they are scary to me!

[MR MAGOO]

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]

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]

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]

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]

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]

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]

Hey we had a top speed of 112 out of my 26 3 weeks ago at an idle, Talk about a thrill ride!

[boldts]

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