Speedometer

Noddy · 18 August 2006, 12:55

I have just bought a new Rib which has a hole in the dashboard measuring 87mm. It is obvious that it once contained a speedometer and there are several on the market that would fit. The seem to come with a "hose and pitot" which I believe must be some sort of transom fitting?
First question - are they easy to fit?
Second question does the "hose" have to go through the transom or can it be bent over it?
I cruise regularly in Chichester Harbour and, judging from previous posts, some sort of speed measuring device is a must??
Thanks
Martyn

slimtim · 18 August 2006, 13:15

I have a plastimo one which is actually made by teleflex. The pitot tube thingy mounts on the transom (dead easy to fit, screws and sikaflex. Just make sure its straight)and I have routed by tube up and over the transom and back down the other side. Having done this, I did think that in theory the water could shoot far enough up the tube to get over the transom and would then be trapped in the tube. I did however think that if this had happened, the speedo dial would be stuck at a certain speed as the pressure in the tube could not be relieved.

Anyway, my one is pretty crap, it only works when going a decent speed (ie doesn't work at all at displacement speeds, therefore would probably be useless if you want to keep to the speed limit in a harbour) and when it does it jumps all over the show and under reads quite a lot. It does however balance out my rev counter and one can never have too many dials, especially if they light up

Tim M · 18 August 2006, 15:52

In my experiance they are useless under about 10 knots. A gps would be a better way of checking your speed in a harbour.

I fitted one in Cormorant by drilling through the transom and then sealing it. I prefer this as it looks tidier and as long as you are libral with the sikaflex and put a little cover fitting thing over both sides water ingress shouldnt be an issue.

Edit: some engines have built in pitots. Might be worth checking yours....

BogMonster · 18 August 2006, 16:58

My engine has a pitot speedo pickup and it is totally useless! It reads nothing at all when you first set off, if you go up to about 30 knots it gradually catches up after a few minutes and then reads more or less accurate, then when you slow down it takes ages to drop back to zero again.

It is a complete waste of space, so I use the page on the GPS (Garmin GPS72) with a big speed readout at the top, on the GPS72 this fills the top 1/3 of the display and is easily readable even when bouncing about a bit.

I suppose the only disadvantage of the GPS72 is it is easy to nick, as it just sits in a plastic mount and all you have to do is undo a thumbscrew, flip a locking thing and off it comes (or just rip it right off!) but it is also easy to remove when you leave the boat.

I've calibrated my other GPS (an eTrex) against a measured mile and the error is less than 0.5% so you can't ask for much better than that

Get a clock, or a barometer, or something that actually works, to fill the hole

Limey Linda · 18 August 2006, 19:46

Suggest you mount a photo of your girlfriend in the hole; you will get more use out of it but maybe a bit of welly. Why do you think you need a speedo in Chichester Harbour? All you need is common sense and that is free !!!!
Regards, T.

Tim M · 18 August 2006, 20:02

It could make a good cup holder. I've just put one on my boat. Very handy for putting vhf, mobile or drink in!