Any GPS experts? cuz.....

[lilrick]

I want to know if GPS's are ever WAY off like 5 mph or more.After speaking with a couple of fellas at the races this weekend, I think my GPS is LYING!! I reset it the same way after 4 races this weekend . The first three races seem fairly accurate. Just curious.

[sanger rat]

Put in some fresh batteries. They seem to read a little slow when the batteries get low. Thanks for the info on the heads.;)

[Morg]

Used to use my e-trex a bunch for tuning. It would read very consistent. You would always want to back up any speed, make sure it is not a fluke. And like mentioned, the GPS needs to "catch-up". You need to hold your top end speed.
BTW- My consistent readings were in the 80 mph range. I don't know if the readings loose accuracy above 100mph.

[Fiat48]

I wonder about this also. Good thread.
Does anybody have a time slip.....and their comparable GPS reading. Also what brand GPS if it makes a difference.

[lilrick]

Used to use my e-trex a bunch for tuning. It would read very consistent. You would always want to back up any speed, make sure it is not a fluke. And like mentioned, the GPS needs to "catch-up". You need to hold your top end speed.
BTW- My consistent readings were in the 80 mph range. I don't know if the readings loose accuracy above 100mph.
My reading seems TOO fast ,not slow. I'm stumped.

[sanger rat]

My reading seems TOO fast ,not slow. I'm stumped.
You must have the V-drive model then.:D

[Fiat48]

You must have the V-drive model then.:D
LOL. And here comes the guys "How much will you take for that GPS???" :D

[dmontzsta]

Is it that hard to believe? :D
It just feels too easy with a prop boat doesnt it? too good to be true or something. ;) Buy a decent hull with a decent motor and run triple digits, think of how much it would have cost to with any other type of propulsion.

[steelcomp]

Rick...after talking with you on Sat. I was thinking about this...I don't see any problem with what your GPS read. You found some nice water and stood on it...your boat had better run that number if you want to be any where near competitive. I think you just started to get a little more comfortable, that's all. Next race you'll be expecting numbers like that...or better. Again, good job this weekend. :D

[QuickJet]

Is it that hard to believe? :D
It just feels too easy with a prop boat doesnt it? too good to be true or something. ;) Buy a decent hull with a decent motor and run triple digits, think of how much it would have cost to with any other type of propulsion.
Ha ha ha, I see the lit match flying towards the puddle of gas......:D

[MAXIMUS]

Is it that hard to believe? :D
It just feels too easy with a prop boat doesnt it? too good to be true or something. ;) Buy a decent hull with a decent motor and run triple digits, think of how much it would have cost to with any other type of propulsion.
:notam: :notam: :notam:

[lilrick]

Is it that hard to believe? :D
It just feels too easy with a prop boat doesnt it? too good to be true or something. ;) Buy a decent hull with a decent motor and run triple digits, think of how much it would have cost to with any other type of propulsion.
Don, it just doesn't work that way. I don't get it. It was definitely a fluke.

[Ralph Brunt]

rick the pick on your gps came out good i'll post it tonight after work.
ralph

[gn7]

Don, it just doesn't work that way. I don't get it. It was definitely a fluke.
never seen one read fast, we have one that ALWAYS reads slow if you would like to borrow it for april, warning though, it reads like 10-15 slow. I was going to send it in under warranty then figured some nost. guy might like it. We always do testing with two now.

[dmontzsta]

:notam: :notam: :notam:
:D
Sucks about your boat this weekend Maxi. I am sure you will get that sucker ready to go.

[RitcheyRch]

Im watching this as well since trying to decide which Garmin to get. Kind of stuck between the Garmin Etrex Vista C and Vista CX.

[dmontzsta]

Come to think of it, I think my GPS is off to. It actually turned an 85mph boat into a 54mph boat once. :)

[Emanon Performance Marine]

Rick you laid down a great pass on the back strieght-a-way and hung the the other PS boats early in the race, so I think it was totally correct.
BTW - Good job out there this weekend !

[VDRIVERACING]

Rick - You can borrow my GPS at Parker. It seems to be pretty much on the money, and I cross reference it to my water-speedo.
As far as your high speed, think about how the top guys look so smooth when they are really going fast. Where guys like Dave Bryant live in that zone, many of us with less experience find ourselves there by circumstance, only then realizing that going fast is not the result of a death-wish hammer-down when you're out shape, but rather guiding your craft to that ideal water-hull relationship.
So enjoy the moment. You looked good out there and drove what the circumstances allowed you to. A pretty successful outing!

[Racey]

Garmin Gps is the only way to go for handheld. and if it has a top speed recall it only takes a split second going that fast to hold your top speed, the gps is actually calculating your speed a thousand times a second, the display might only update every half a second or full second, this helps lengthen battery life.

[dmontzsta]

Rick, I will bring my GPS too if you want, just let me know.
It has only been used around 3x.
Lets all bring out GPS units out so Rick can use them all, to put his doubts to rest! :D

[Emanon Performance Marine]

Too many GPS units may slow his ass down. But he is welcome to use mine anytime.

[cyclone]

Rick,
I use a cheap Garmin gps attached to my steering wheel when i'm at the drags and 9 times out of 10 it matches what the NJBA timing system says my speed is. The most i've ever seen it differentiate from the njba clocks during a 9 second quarter mile run is 1/2 of a mph. hope this helps.
-mike

[dmontzsta]

Too many GPS units may slow his ass down. But he is welcome to use mine anytime.
The boat is already in pain when he gets in the seat. :)

[Moneypitt]

I think a little math work is in order. I think Rick told me on Thursday the boat has 18 gears...........A little deep for that kind of speed unless it has some kinda magic prop on it, (which it may).....A quick guesstamation, 18s, 16 pitch (which is also a guess) would come out somewhere around 8800!!!!!!! to reach 110.......I don't have the formula handy, so someone else play the numbers game here and ballpark the possibilities..........MP
PS: Regardless of how this all figures out, Rick had a very successful 1st outing, great job, kept the prop down, and ran a 4 lap race with JUST 8 turns......

[Carnivalride]

I think a little math work is in order. I think Rick told me on Thursday the boat has 18 gears...........A little deep for that kind of speed unless it has some kinda magic prop on it, (which it may).....A quick guesstamation, 18s, 16 pitch (which is also a guess) would come out somewhere around 8800!!!!!!! to reach 110.......I don't have the formula handy, so someone else play the numbers game here and ballpark the possibilities..........MP
PS: Regardless of how this all figures out, Rick had a very successful 1st outing, great job, kept the prop down, and ran a 4 lap race with JUST 8 turns......
18's & a 16p prop will run 110mph at 7200rpm with 15% slip.
engine rpm x gear / (1056/prop pitch) = theoritical mph
actual mph / theoritical mph = efficiency

[Speedin' Ian]

I know runner bottoms are a lot different, but we bought a motor from T-bag last year and I believe he ran 140+ with 22's, so I don't see why 110 with 18's wouldn't be possible.

[lilrick]

Thanks for the replys guys.The boat has 22's in it and an 11x16 prop. I'm not sure what the RPM's were. Too scared to look!!

[Carnivalride]

Thanks for the replys guys.The boat has 22's in it and an 11x16 prop. I'm not sure what the RPM's were. Too scared to look!!
lilrick,
with 22's and an 11x16
7000rpm would be about 110mph with 15% slip
7300rpm would be about 110mph with 20% slip

[riverbound]

I have had my GPS read high twice. so although rare it is a possiblity.

[Flat Hall'N]

lilrick,
with 22's and an 11x16
7000rpm would be about 110mph with 15% slip
7300rpm would be about 110mph with 20% slip
Carnivalride,
What kind of formula are you using to get these #'s? I would like to figure out my estimated mph with my set-up since I didn't have a gps on board.

[dmontzsta]

lilrick,
with 22's and an 11x16
7000rpm would be about 110mph with 15% slip
7300rpm would be about 110mph with 20% slip
That sounds about right then. That motor should see close to 7k.

[Carnivalride]

Carnivalride,
What kind of formula are you using to get these #'s? I would like to figure out my estimated mph with my set-up since I didn't have a gps on board.
Flat Hall'N
This is the formula:
engine rpm x gear / (1056/prop pitch) = theoritical mph
example: 7000 x 1.18 / (1056/16) = mph
8260 / 66 = 125.15mph this is theoritical so multiply by .80-.85 to get estimated actual, in this example 100.12mph - 106.38mph
actual mph / theoritical mph = efficiency
If you have a computer with excel spread sheet capabilty you can insert it or I could email you a gear chart.

[Flat Hall'N]

Flat Hall'N
This is the formula:
engine rpm x gear / (1056/prop pitch) = theoritical mph
example: 7000 x 1.18 / (1056/16) = mph
8260 / 66 = 125.15mph this is theoritical so multiply by .80-.85 to get estimated actual, in this example 100.12mph - 106.38mph
actual mph / theoritical mph = efficiency
If you have a computer with excel spread sheet capabilty you can insert it or I could email you a gear chart.
Much appreciated Carnivalride, this is great. I'll go ahead and plug this into an excel spreadsheet. Thanks again!!

[Moneypitt]

Rick, don't change anything......nothing........Just learn to turn that thing and, based on the math, you'll be running right along with, or pulling away from the SS80 boat. That is some kinda D'Cucci hull, 110 "right outa the box" so to speak.....Just weld the plate adjusters in place, cause you never want to change that set up. Then call Dave Rankin and let him know you're coming, and all those years of testing and trying were a waste of his time........Oh yeah, one more thing, go buy a lottery ticket, just one, that's all you'll need......Ray

[superdave013]

Ray, he's running Motor Magic power. He might have some left in it for all we know. :eek:

[VDRIVERACING]

I think a little math work is in order. I think Rick told me on Thursday the boat has 18 gears...........A little deep for that kind of speed unless it has some kinda magic prop on it, (which it may).....A quick guesstamation, 18s, 16 pitch (which is also a guess) would come out somewhere around 8800!!!!!!! to reach 110.......I don't have the formula handy, so someone else play the numbers game here and ballpark the possibilities..........MP
PS: Regardless of how this all figures out, Rick had a very successful 1st outing, great job, kept the prop down, and ran a 4 lap race with JUST 8 turns......
Using 20% slippage, I came up with 7700 rpm. Is 20% about right?
Rick - what's yur prop??? what RPM do you think you could pull?

[Emanon Performance Marine]

He is not sure on the RPM
Thanks for the replys guys.The boat has 22's in it and an 11x16 prop. I'm not sure what the RPM's were. Too scared to look!!

[Roaddogg 4040]

Hey Rick... that GPS must be the same one they use to test the E-Bay boats that we see for sale...:D
Steve

[lilrick]

Hey Rick... that GPS must be the same one they use to test the E-Bay boats that we see for sale...:D
Steve
I was thinking the same chit! :D

[Carnivalride]

Using 20% slippage, I came up with 7700 rpm. Is 20% about right?
Rick - what's yur prop??? what RPM do you think you could pull?
With 18 gears and a 16 pitch prop that would be right.

[Fiat48]

Rick,
I use a cheap Garmin gps attached to my steering wheel when i'm at the drags and 9 times out of 10 it matches what the NJBA timing system says my speed is. The most i've ever seen it differentiate from the njba clocks during a 9 second quarter mile run is 1/2 of a mph. hope this helps.
-mike
Please list the model number so I can buy the exact same gps unit. Thanks in advance.

[lilrick]

I use the Garmin etrex , it's blue and water resistant. It also floats.

[infotraker]

Anyone used their gps for altitude reading ? I was at about 3000 feet up in the mountains on a hike and the gps altitude reading would jump around going up and down when I was not moving. It is a garmin etrex legend.

[rrrr]

I use the Garmin etrex , it's blue and water resistant. It also floats.
Maybe the boat went that fast because you skipped breakfast.....:jawdrop:
Rick, my etrex has always worked fine.....there really isn't any way for it to not work and still show a speed. It won't let you use it unless it sees at least three birds.
Did you go into the config menu and clear the previous max speed? Gotta do that every time to get correct top speed tuning info.
I can't tell you how...... http://www.***boat.com/ubb/graemlins/idea_2.gif Wiggle the joystick and push the buttons until it gives you what you want.......just like a woman. :D :D

[RitcheyRch]

I just picked up a Garmin E-Trex Vista CX.

[lilrick]

Maybe the boat went that fast because you skipped breakfast.....:jawdrop:
Rick, my etrex has always worked fine.....there really isn't any way for it to not work and still show a speed. It won't let you use it unless it sees at least three birds.
Did you go into the config menu and clear the previous max speed? Gotta do that every time to get correct top speed tuning info.
I can't tell you how...... http://www.***boat.com/ubb/graemlins/idea_2.gif Wiggle the joystick and push the buttons until it gives you what you want.......just like a woman. :D :D
I reset it all four times I went out.I guess I just can't believe I went that fast.

[GofastRacer]

I reset it all four times I went out.I guess I just can't believe I went that fast.
You might have hit some good water and it freed up the boat???..

[Fiat48]

Just don't change anything and take it to bakersfield and run it through the lights. That will tell you.