Speedometer not working, yet another one

[badrano]

I've been trying to figure this out but I'm throwing in the towel and asking.

I've tested the tubing between the sterndrive connection and the speedometer and that line is all clear. I pretty much figure the clog is in the lower unit. Now that I have the sterndrive removed, I have much easier access to the connection point on the lower unit. I've tried to blow air back through the connector but can't seem to clear the clog.

Would the next step be to take a piece of wire and start poking at the pickup hole and/or from the connector?

 

[harringtondav]

The speedometer is just a low pressure air gauge. While you have the drive off apply a VERY low amount of air pressure into the pickup hose. Use a syringe or a bicycle pump, even your mouth should be enough. The gauge should react, and verify that it's good.

Most of the time there is a blockage in the pickup hole at the front of the lower gear hsg. I use a cordless drill with a 1/16" drill to carefully remove the blockage. Careful means don't break off the drill. Normally when you're on a trailer or lift the water in the speedo hose will start weeping out, and eventually back flush the clog.

I rigged up a flushing tool. I bought a transom side speedo hose connector and wire tied it onto a piece of clear plastic tubing. I bought a male garden hose connector with a pipe thread, and adapted it to a hose barb the same size of the clear tubing. Wire tie the tubing to this barb also. You can use the fitting off your speedo hose also. I run into trash frequently, so I just bought one to keep this tool on the shelf.

Connect to your garden hose and the lower gear case speedo fitting. Crack the hose bib valve open. The pressure will build to house pressure. If this doesn't blow out the clog, keep working with the 1/16" drill. I've had some stubborn clogs, but they all gave up eventually.

If the clog won't budge, remove the speedo connector from the gear hsg. There is a long drilled hole that goes down to intersect with the pick up hole. You can try probing with a long coat hanger wire, while working the pick up hole. I've never had to go this far, but it should work.

 

[alldodge]

Get a 3/32 drill bit and with your hand (pliers, vise grips) insert into the hole and rotate to clean. A buddy made me one and used wooden file handle, works great

 

[drolds72]

I had to attack a clog from both the pickup hole and from the top speedo connector. Instead of a drill bit, I stripped the insulation off a 12" piece of 14 gauge romex. hit the end with a hammer to flatten it, and used bench grinder to shape tip into a spear. Long enough to spin from the connector side straight down and "drill" out debris.

 

[Scott Danforth]

google pin vise

next to a tool box full of hammers, a mechanics best friend.

 

[badrano]

Thanks for all the feedback. Time to start poking around in a hole.:facepalm:

 

[Walt T]

Yep, might have hit a piece of wood and really compacted it in the hole. Don't be afraid to clear that hole with a drill, just remember the drill will go through wood right quick any real resistance is the metal of the drive and it's best you back off.

 

[wahlejim]

I highly recommend switching over to a gps speedometer. There are hundreds of styles available, and some pretty advanced ones with a digital display that will keep track of distance, peak speeds, etc. Designed to fit right in your dash.

 

[badrano]

I highly recommend switching over to a gps speedometer. There are hundreds of styles available, and some pretty advanced ones with a digital display that will keep track of distance, peak speeds, etc. Designed to fit right in your dash.

You just had to make that post. This isn't helping the total cost of my wish list. Now I will spend time at work googling these speedo's instead of doing my job.

 

[Walt T]

It's cold outside today, So I'm spending the day seated at my toolbox playing the old arcade game Space Invaders.

 

[achris]

It's cold outside today, So I'm spending the day seated at my toolbox playing the old arcade game Space Invaders.

Yep, cold here too... Only going to be 22C (71F)... Brrrrr.

Chris.......

 

[achris]

I highly recommend switching over to a gps speedometer. There are hundreds of styles available, and some pretty advanced ones with a digital display that will keep track of distance, peak speeds, etc. Designed to fit right in your dash.

As nice as they are, why not just use the speed indication in the GPS plotter? Or download GPSTest onto your phone? One of the best GPS programs. I was so impressed I paid (99c) for the Pro version. It even has a HUD, so you can just throw the phone on the dash and read it directly in the windscreen reflection.

Chris.............

(some screenshots)

 

[jimmbo]

If the river/lake has any current, a GPS is going to show a speed difference when running with or against said current. It will be measuring ground speed not water speed. So a boat may do 50mph in one direction but only 30 in the opposite way if the current is 10mph

 

[achris]

If the river/lake has any current, a GPS is going to show a speed difference when running with or against said current. It will be measuring ground speed not water speed. So a boat may do 50mph in one direction but only 30 in the opposite way if the current is 10mph

And your point?

(BTW, those posted speed restriction signs, they are speed over ground, not speed through the water. So the GPS is better than the pitot tube speed anyway...)

 

[jimmbo]

My point is GPS as a speedometer is not always what people think it is

It can also throw a real wrench into some people calculations when it come to prop slippage(I am going to love that one) depending on the current and direction the boat is traveling. Now days there are a lot of people praising the GPS over the pressure gauge speedo, but it is not flawless. On land, a hill or valley will lead to inaccuracies too.

 

[achris]

My point is GPS as a speedometer is not always what people think it is

How so? It's tell you how fast you are going... And at the end of the day, that's what people want to know.

Yes, GPS is ground speed, pitot tube speedo is water speed... And if you're using a pitot tube speedo in a river running with a 4 knots current and you're in an 8 knot speed restricted zone you're doing 12 knots, the pitot tube speedo will still indicate 8 knots and get you a fine, the GPS will not. The only times a pitot tube speedo is of any benefit is in fuel consumption calculations if you're basing it on distance through water, and in some sports where water speed is required, like bare-foot skiing... Other than that, toss the pitot tube speedo over the side, it's useless. And it's useless below about 6 knots anyway....

Chris.....

 

[achris]

My point is GPS as a speedometer is not always what people think it is

It can also throw a real wrench into some people calculations when it come to prop slippage(I am going to love that one) depending on the current and direction the boat is traveling. Now days there are a lot of people praising the GPS over the pressure gauge speedo, but it is not flawless. On land, a hill or valley will lead to inaccuracies too.

On land, yes hills, valleys (and they have to be quite big) , and city skyscrapers mess with the signals.... But I haven't seen that many skyscrapers 30 miles out to sea....

 

[harringtondav]

I run by tach, and the amount of bounce I can tolerate (more the wife), and my gas gauge if I'm on a long trip. I have a std. pressure speedo. If I hit trash and the speedo fails, I'm OK. But I clear it out before towing one of my fussy skiing or wake boarding fiends. Or not. Thumb up or down still works. I'm OK with 30/30 cruising. I know how fast my boat can go. I 'm generally not in a hurry.