What is this?

[Bucks45]

I have a 1987 Searay S-23 with a 5.7 Merc, Alpha I. I will be the first to admit that I know very little about boats. I was replacing the transducer (putting in a new fish/depth finder) and on the opposite side of the drive I have this. What is it? As always, thanks for the help.

Aaron

 

[marcortez]

Re: What is this?

Speedometer pickup.......

water is pushed in, and up the tube, which makes your speedometer gauge register a "more or less" over ground (water) speed.

Worthless in my opinion, and if that was my boat, it would all come off and donated to the nearest plastic recycler.

A GPS unit is FAR better at giving you accurate speeds.

 

[whatshisname]

Re: What is this?

that is the speedometer sending unit

 

[Bucks45]

Re: What is this?

Thanks guys...........I appreciate it. Another thing learned from Iboats!

 

[Fisherball]

Re: What is this?

It's called a pitot tube. I think they work by vacuum, drawing air out of the tube as it travels through the water. The ones used in airplanes work by air being forced into the tube. Not very accurate but close enough for me.

 

[RotaryRacer]

Re: What is this?

I don't get why people are always saying pitot speedos are worthless.

Both of my boats pitot speedometers are within .5 MPH of GPS at all speeds and at WOT they are both pretty much dead on.

 

[madurodave]

Re: What is this?

I don't get why people are always saying pitot speedos are worthless.

Both of my boats pitot speedometers are within .5 MPH of GPS at all speeds and at WOT they are both pretty much dead on.

ditto

 

[BTMCB]

Re: What is this?

Agree with Rotary.....my speedo seems to be pretty accurate too. GPS is quicker to record maybe when I hit the throttle but once at cruise or at WOT the speedo catches up and is usually right on with the GPS or at least within 1-2mph more often than not.

 

[cr2k]

Re: What is this?

No vacuum involved. Water is pressured in to the forward facing hole in the end and sent up the hose to the speedo which is actually a pressure gauge calibrated in MPH instead of PSI. You can test your speedo by putting an air hose to the hose or the pitot hole and seeing the gauge move. If they quit working you pull the hose from the speedo and blow air back out the pitot.

If the hose breaks in the boat you have a fountain!

 

[marcortez]

Re: What is this?

I don't get why people are always saying pitot speedos are worthless.

Both of my boats pitot speedometers are within .5 MPH of GPS at all speeds and at WOT they are both pretty much dead on.

Until it hits a floating object and knocks off.......
Or gets loose in the attachment and kicks up at plane speeds.
Or clogged with moss, algae, pond scum, mosquito larve, kelp/seaweed fronds, or any manner of floating debris.....that is guaranteed to find it's way into little holes that drag just below the surface.

 

[Silvertip]

Re: What is this?

If your water is so scum filled and littered with debris speed is one of the last things I'd be worried about. Clogging of the water pickups on the engine would be higher on my list of things to worry about. I too have no problem with pitot driven speedometers. Simple, inexpensive and reliable. Yup -- I also have GPS but use it for navigation as speed is not a major part of my boating activity.

 

[Fisherball]

Re: What is this?

I didn't know they were that accurate. Part of that reputation could be that if you are in moving water sitting still it will read the speed of the current. The lakes I use in central Ohio don't have much current so the readings have always been close enough for me.

 

[JimS123]

Re: What is this?

When we were kids we used to drill out the hole in the pitot a little bit. More pressure of course, the gauge read higher and the boat went faster.

Its true! Our girlfriends could see the dial with their own eyes!

 

[QC]

Re: What is this?

Mine have been accurate as well, however I have used the Merc built in pitot not the transom mount type. Bravo and Alpha both within 2 or 3% of GPS. A couple of points:

1) Someone posted that pitot type speedos read speed over the bottom. That's what a GPS does, definitely not what these speedos do . . .

2) See #1, the value of these things is that they read water speed. Paddle wheel types are more accurate, but if you are dialing in a propeller, for example. And were making runs up and down a river or other current, GPS is not the device you want to use. One of the places I boat averages 3MPH of current. Funny but my boat runs better downriver there than anywhere else . . .

 

[cr2k]

Re: What is this?

I can't believe there are 14 posts on this.

 

[QC]

Re: What is this?

Ever seen an oil thread?

 

[smokeonthewater]

Re: What is this?

or a "can I tow this with this" thread

 

[Bucks45]

Re: What is this?

I know that you guys like to talk boats, but I had no idea this would create a debate! Thanks again for the help.

 

[cr2k]

Re: What is this?

Don't sweat the petty stuff....

And for darn sure don't pet the sweaty stuff.

 

[H20Rat]

Re: What is this?

my pitot tube is MORE accurate than any gps at figuring out how fast my boat is going on the river!