Speed measurement tools

Yea, agree,
I was itchy to upgrade my instruments until I saw the price tag. So I sat myself down and said justify what you need. Depth gauge, knotmeter, GPS, timer, compass... good to go.
john

My 2-cents.

It depends on what you are using it for. A GPS is ok if you are navigating but if you are trying to race you really need speed through the water (defined as boat-speed) from a log transducer. The reason is twofold. First, GPS speed isn’t sensitive enough. Second, GPS speed is S.O.G. (speed over ground) which isn’t really what you want to help you steer correctly. S.O.G. includes current effects. By the way, for similar reasons the GPS shouldn’t be used as a racing compass to keep track of headers and lifts. GPS isn’t sensitive enough and it provides C.O.G. (course over ground) not heading.

I have a classic Nexus system with speed, wind, wind direction, and depth. I also have a KVH “Sail-Comp” electronic compass and a simple hand-held GPS. Both the electronic compass and GPS are tied into the Nexus system.

For racing, the most important data to use while steering is the boat-speed and compass heading. I only use the GPS to tell me distance and direction to the next way-point because our marks can be hard to see. The wind data is interesting but not really necessary for the type of racing we do.

The boat came with Nexus and KVH. I only added the GPS. If I were to do it over again, I’d look at both the Tactic and the Nexus II. I believe both are “wireless” and therefore are much easier to install. In both you can start simple, with the log transducer and depth only, and add elements on as you see fit. In either case, you can very easily send a single from a hand-held GPS. Since it’s much easier to enter information on the hand held GPS than into the Nexus or Tactic instrument packages, I would not bother with the Nexus or Tactic GPS transducer.    

Depends on your budget Bill,
I've had knotmeter failures on 2 different boats and in both cases I did a google search and found the manufacturer. In both cases the technician told me I could send parts in for verification and options for repair or discounted replacement.
That said, my knotmeter is on the fritz again. Maybe it was damaged when we were surfing at 16.3 knots.
Anyway, you should have a handheld GPS regardless of your knotmeter situation and that will get you by for a little while.
If you end up replacing your knotmeter, I would get equipment that can be integrated to create a system. Then you can add on instruments for wind speed and direction if you want. Again, if you contact the manufacturer of your existing unit, they may give you a discount on an upgrade.
john