boat speed

[bowfin]

hey guys
just a few question for ya i got a used crestliner 2006 1800 mirage with a 150 opti my question is when wot the speedo on the boat reads 46mph and on the fishfinder its reading 52 mph which is more accrurate speed the speedo for the fishfinder is one of those pinwheels on back of boat the ff is a eagle 480 which i like for now my next one will have the built in gps will have to wait for a few yrs for that one motor is running at 5200 rpm at wot. to me the thing just rips compared to my old 84 bluefin with a 115 johnson lol
thanks guys

[staylor]

...you need a check with a GPS for true speed.
Doug

[REG]

See if you can borrow a handheld gps from a friend - it doesn't need to be fancy - just needs to give you a mph reading and then you can see which one of your gauges is the most accurate.

I've always wondered about using a car gps plugged into the 12 outlet - it might freak since you're not on a road, but would it still give you speed?

[darin]

I've taken my Nuvi 205 out with me and it gives me the speed... Most say neither of those are accurate, but like was said, check and see with the gps. I know some days my speedo will be close and other days it's way off or not even working... probably clogged.

[lundeepv]

GPS is the only true way to gauge a boat's true speed.

[Kevin R]

Here is what I had F150 Yamaha on 18ft Scout Dorado with electric Jackplate. Pinwheel depthfinder speed 68mph, Yamaha speedo 49-52, GPS speed was 53 MPH. Checked with other GPS & 53 MPH. GPS should be true speed.

[yarcraft91]

A car GPS will not only display speed, but if you have a compatible lake contour map chip, the car GPS will display the maps, too. I've done that with my Garmin Nuvi 650 and a Lakemaster chip meant for Garmin boat GPS systems.