Pontoon Boat & Deck Boat Forum

How much difference do you guys observe between the GPS and your boat speedo? When my GPS shows around 24 my speedo shows about 15. I know the speedometers are notoriously inaccurate, but is there anything I can do to make it any more accurate. I don't really have a reason as I normally have my GPS with me and I really don't have a need to know my speed except for curiosity. I have what I think is a speed sensor on my left pontoon. I also have a rubber tube going to my motor that is labeled as a speedometer tube on the parts diagram. I had to disconnect it when I dropped my lower unit to replace the water pump. Which of these should I screw with to see if I can improve the speedo reading? I'm assuming the speed sensor hanging off the pontoon wouldn't be there if it wasn't connected to the speedometer. Anybody ever have any luck improving their speed reading without replacing everything?

Try the one on the engine. They are usually better.
They take a cleaner sample of the water flow.

My boat dealer said to blow out the tube with air.

I just use my GPS speed, it is accurate.

The Party Cruiser didn't come factory with a speedo

I use GPS..

On my Starcraft the Speedo is always reading lower than GPS.

Your first picture is the pickup for your spedo. You can try running a fine strand of wire through the little hole in the bottom of the plastic. Disconnect the rubber hose first though. Sometimes crud will get in the little hole. You don't want to push any crud up into the rubber hose. However they are not very accurate. My Four Winns Spedo reads 48mph WOT and GPS says 54 mph.

A new water pick up is very inexpensive, thy a new one if blowing in the tube does not work,

Using the pickup on the engine my speedo is pretty close to the GPS when everything is clean and the motor is trimmed flat. All of them do plug up over time.

From a previous post I took out my gps on the pontoon and checked my speed against the GPS and found the speedometer was exact with the gps. Kind of surprised me since most said the speedometers were not accurate. Oh well, good for me.

Where is the pickup? Pitot or on the foot of the motor?

So if I can't get the speedo pickup on the pontoon to function what would I have to do to use the one on the lower unit instead? I'll have to get out the ole' exploded parts diagram and see what I can figure out as far as where the tube runs. I wonder why the original owner didn't use that setup? Oh well, something else to take up my time and cost money My wife asked me last night when I came in from taking pictures of the boat, "Is there SOMETHING ELSE wrong with the boat now?". No, dear. Just some improvements that could be made. You'll appreciate them come this summer

The speedo tube I'm referring to on the motor is represented by part #18 in the attached diagram. I've looked at the other diagrams and I can't seem to figure out where the tube goes from there. I guess I'll try tracing it this weekend.

There should be a stub on top of the cavitation plate or in that area where you slip on the hose to the gauge.

Greg,
That would be #19 on the diagram above? I can just take the rubber hose off the existing pickup on the pontoon and run it to the stub on the motor? What is the function of the existing hose on the motor? Do I just do away with it? Thanks.

That is the pickup output hose. I put one of those hose couplers on top of that right to the speedo hose. I think the coupler was in the rigging kit that comes with the motor.

pelicantooner wrote:From a previous post I took out my gps on the pontoon and checked my speed against the GPS and found the speedometer was exact with the gps. Kind of surprised me since most said the speedometers were not accurate. Oh well, good for me.

Mine is very close also and I have a Yamaha too.

If anybody has a picture or diagram of how their speedo cable connects to the motor it would help a lot. I'm a visual learner