Garmin etrex, zip tied to the steering wheel. 

I trust the max speed if the number looks reasonable.  I've seen it say 168mph one day after bouncing over some rough water....obviously, that number is bs. 

I tried same thing with my phone too, but numbers came out different when we were on the boat. 

Maybe 15 to 20 mph slower. When in my vehicle on the freeway right on. I don't know what happened on the water. They need a boat setting on the app. I used the garmin etrex from a buddy before and got a more accurate reading. It will give you the avg. and top speed.

Do you guys trust this max number? Like LBHSBZ I too had my Etrex spike and the Max speed recoreded at over 130... Needless to say I didn't consider this a reliable number. I also saw a 64 while driving approximately 40 on the street.

We aren't having any problems... we just aren't drinking the kool aid. If we did I would have a 130mph jet boat. My brothers gps data logger does more than just give gps numbers. It also logs g-force and location. It is equally accurate by comparison to my Etrex. By logging the boats speed several times per second we can rule out the split second spikes in speed that are not accurate.

My concern in asking is regarding people who just spew out the max speed number recorded by their gps.

I have a magellan triton...its been great on the freeway with my truck, but I seem to always leave it in my truck when I hit the lake...the gps apps I have tried on my phone have all been 2-3 mph slow vs my speedo...also I compared it to the clock things you see on the side of the road and the same deal 2-3 mph slow...you guys can borrow my gps and compare numbers...if your looking for max speed borrow rays gps

Sent from my Samsung Galaxy S 4G

Boost has a good max speed GPS too 

Who's "boost"??

I am going to get rid of my logger! All it has proven to me is that it gives consistent real numbers! I am going to get 5 hand held units and when one of them gives me a number that I want, I will use it. I have no use for real data that can be logged and compared to equipment changes! I just need a number.

If I would have realized that people are using peak numbers I would have just bought a row boat and kept the handheld gps with me long enough for the piece of $#!+ to give me the number that I want.

The purpose for the logger is to have a base line that I can compare all of my changes to. That way my speeds are valid! The logger monitors 5 times per second. If I go from 50.6375 to 74.6327 for two tenths of a second I can ignore the 74.xxxx. That way, if I put a new bowl on the boat and the new log reads 56.6537 with a .2 second peak of 68.7585 I know that I have an increase of 6mph not a loss of 6mph.

My boat currently runs 56.xxxx mph. I would love to get a bunch hand held gps units together and compare their peaks on the same run.

Using the Etrex we cruised at 38-44 mph for about ten minutes straight in the truck. It was "dead on" the whole time with the truck speedo. Somewhere in that timeframe it peaked at 67mph.
While we were on the boat it was very consistent and appeared to be accurate the entire time. It peaked at 74 mph. Do I have a 74mph boat? 74 seems very reasonable for a 454 bowtie aluminum heads .640 lift cam blah blah

Anyone with a gps 75 plus boat want to run? I will be at mead August 20 at Dawn. It would be cool to put the handhelds together to see what they do.