How to Unclog Speedometer Tube?

[pstephens46]

Do they even make a 1/6" bit? Seems like that would be too big. But, as others mentioned, the idea is to do it BY HAND.

I have no clue what engine you have, but...

-- Drill bits are magnetic.
-- Find the next connection point for the pitot further upstream, open the connection (cut and splice tube, if you want, or go all the way to the speedo) and blow compressed air into it.
-- Combination of the above two.
-- Cut the pitot hole slightly larger (cut off wheel or hacksaw) so you can grip the bit.

Perhaps the lower unit can be removed and some string trimmer line be fed down the backside and push the bit out enough to grab with pliers?

[fairdeal]

used a 1/6" drill bit to unclog mine using a hand drill it broke off level and cannot grab with anything including a magnet any ideas ?

disconnect the hose currently leaving the motor cowling and connect this instead:

transom mount speed pickup

https://www.boats.net/product/yamaha/688-83556-00-00

[TownsendsFJR1300]

I "T"eed into the plastic line up in the center console (before the speedometer). Then I put a Schrader valve into that line.

With a small 12 volt bicycle air compressor, it clips onto the Schrader valve .

Power it up and it blows ALL the water, debris out of the line. The speedometer will read about 17 MPH while the rest goes out the pitot opening.

**As yours is clogged now, there's a connection just past where all your lines exit the engine including that plastic, speedometer tube.
I'd pull that loose and try compressed air while running a fine drill bit (by hand) or "JET cleaner" thru the small pitot hole.

Using a hose (I use an old clothes washer hose-rubber, about 3/8"), cut the V in one end and hook up to the hose. Hold the V tight over the pitot opening and with a hand nozzle, use WATER PRESSURE from the pitot hole to blow loose any debris in there...


That hole likes to corrode if NOT FLUSHED and clog.


For me, I flush FRESH WATER into the pitot hole. Then run the lil air compressor from the console. It pushes all the water out / no corrosion.
The engine is now 12 years old, used in brackish / salt water and with this set up, still works GREAT down to 4 MPH...

You'd be surprised at how much water stays in that line up inside the entire line...

[fairdeal]

I'd pull that loose and try compressed air while running a fine drill bit (by hand) or "JET cleaner" thru the small pitot hole.

that's what he was trying to do, Scott:

used a 1/16" drill bit to unclog mine using a hand drill it broke off level

[TownsendsFJR1300]

that's what he was trying to do, Scott:

Tapping the LU next to the broke bit to loosen it (engine trimmed all the way up so gravity helps) and air pressure may loosen the broken bit.

Even possibly using a heat gun to the aluminum, just to expand enough, again with some tapping may drop the broke bit.

If that doesn't do it, a Dremel taken the leading edge of the hole, cut just enough to loosen the bit should work. As I re-call, that orifice goes in a bit (guessing an inch).

[FabricGATOR]

I remember 'fixing' the leading edge pitot tube when I first bought 'My Jenny' I used a drill bit (in a pin vice, by hand.... perhaps it was a vice grip, but by hand) I had remnants of barnacle built up in there.

My Jenny is now a trailer boat, but had been in the water extensively and the lower units suffered electrolysis, corrosion, and someone painted copperous antifouling on my aluminum engine. Not good practice.

Anyway, first thing, water pumps... while I had the lower off, I tried to unclog the occluded pitot on that engine. I got the front pushed through yet it was still clogged. I removed the hose barb from adjacent to the waterpump/shift rod. I believe what I discovered was a (metric conversion required) 1/4" or 3/16" machined hole down the casting to the point where the pitot enters at a 90º angle. I ran something down there and got it all cleared and it has been working great for several years.

[FabricGATOR]

Now, I mentioned I have corrosion and electrolysis damage. I just happen to have both lowers off to address that this week. I looked at my pitots just the other day while stripping and sanding. I thought I had damaged the tube because I see it is split as I machined the corrosion back.

I do have to say, it sure does resemble a stainless steel roll pin. I wonder if I can put it back in , if I pull it out...
It would/could be a logical manufacture solution to use an ' off the shelf ' roll pin as a liner for the pitot tube.

[99yam40]

roll pins are spring steel and rust, I would not think those would be good to use in a salt water enviorment

[FabricGATOR]

roll pins are spring steel and rust, I would not think those would be good to use in a salt water enviorment

Yes, they are made of high carbon spring steel and rust like crazy. Unless you use the stainless steel ones...
https://www.mcmaster.com/stainless-steel-roll-pins

https://www.mscdirect.com/industrial...-roll-pin.html

https://www.amazon.com/Stainless-Ste.../dp/B00DC5QJUK

[FabricGATOR]

I am getting ready to get back to work on mine here shortly. I'll take a picture and perhaps even give it a tug. Like I said, I am addressing corrosion deterioration in the vicinity of the pitot tube. It would likely make my procedure easier to have it out of the way temporarily.

I just may end up with a transom mount pitot tube when all is done..... I really prefer not to have to though.

[zenoahphobic]

It's the stainless steel pitot tube reacting with the aluminium causing that corrosion you speak of.

Therefore this corrosion could cause a blockage just at the end of the small tube in the casting, I would imagine.

There is no reason this tube can't be replaced with a larger tube, but there is a limit to the protrusion as the altered "aerofoil" will create turbulence that may see less pressure (not more as might first come to mind. Your alternative is to remove the existing tube and restore the foil section and place a hole either side flush just behind the leading edge.

The problem with the old style separate speedo thingy is that they are easily damaged. On smaller boats we would remember how these used to get ripped off in shallow water or reversing, or being kicked up by weed etc. making them not function a lot of the time as well.

[FabricGATOR]

It's the stainless steel pitot tube reacting with the aluminium causing that corrosion you speak of.

Therefore this corrosion could cause a blockage just at the end of the small tube in the casting, I would imagine.

The problem with the old style separate speedo thingy is that they are easily damaged. On smaller boats we would remember how these used to get ripped off in shallow water or reversing, or being kicked up by weed etc. making them not function a lot of the time as well.

The majority of the lower look like Charles Bronson's face where they had painted antifoul on the bullet. I gotta say that I am more inclined to believe it is the copper bottom paint dis-similar metal reaction rather than SS to AlumaMag alloy dis-similar metal. AND electrolysis. They had a solar battery charger panel connected for years while it sat out in the sun.

I had to replace the Armstrong aluminum engine bracket because it was bullet riddled with corrosion also. I poked a #2 phillips screw driver through 1/2" plate section trying to determine how deep the damage went.

Yes, that is my thoughts, if I can remove the pitot tube to repair the foil, and then reinstall it, would be a lot easier than trying to work around it.

[FabricGATOR]

This was the unused PORT engine (CR) pitot tube, so I'll likely not reinstall it. Although to have a spare should the STBD pitot ever become unusable.. IMG_1383.JPG

I did not measure it but yes, it is a stainless steel roll pin. Likely 1/8" X 1/2" (estimate) I will micrometer it if anyone else is interested. IMG_1385.JPGIMG_1386.JPG

Now to discover an alloy filler rod and welding process... Perhaps Oxy/Acetylene and a wire coat hangar...

[DennisG01]

Is that SS roll pin SUPPOSED to be there? I can't say I've ever looked close enough - those ump**** times I've cleared pitot holes on many different engines - but I can't ever recall seeing that. If someone had stuck that in there, it would certainly explain the corrosion issue that is centered around the roll pin. I can't think of any other explanation for the corrosion to be centered around the hole like that. Meaning, that's not normal corrosion - it wouldn't normally be that localized.

[99yam40]

that thing is in need of replacing.
welding corroded cast aluminum is not going to work