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Speedo not working

Acer2428

Acer2428

Member
Just picked up an '81 Predictor.

The speedo doesn't work. The connection to the speedo seems solid and I believe I traced the line correctly. It looks like it goes into the lower unit.

I'm hoping it's just some crud caught in the line, blocking it.

What should I be checking/what's my first step?

Thanks all.
 
I'm no expert, but I'm not aware of any speedo's that operate off of the motor. There should be a plastic, spring loaded pickup hanging off the back edge of the hull somewhere and a tube running from there to the speedo.
 
This would be the speedo line going into the LU, for future ref.

477A5B1D2D75493F81169106C513B085.jpg
 
The speedo's use water pressure to measure speed. You may have trash in the line at the lower unit. What you can do is take the line off at the lower unit and gage, then use compressed air at a low setting to blow air through the line to see if the clog is in the line. If the line is clear, hook it back up to the gage and blow. The gage should move. This will test the line and the gage. Then hook a piece of hose to the connection on the lower unit and use air to blow through. This is normally where the clog is.
 
ohh that's what that tube is on my lower unit. I thought I broke something when I pulled the unit to do my water pump. I don't need it as my boat is using the little plastic thing on the bottom. But its good to know what that was heh.

I believe you would have to remove the lower unit to get to the fitting to remove it. Dropping the lower unit is not hard. You just loosen the nuts and it drops in your hand. Putting it back up can be fun. You have to align the water tube, driveshaft spline and shifter spline as it goes up. But it may be easier just to install one of the plastic pitot things on the back of the boat and routing the tube to that.

Also I wouldn't blow into the tube from the back. I would back blow it from the gauge to the back. As if there was something in the line I wouldn't want it messing up the gauge.
 
I'm going to pull it out from the back of the speedo today. It's hard b/c the steering box is RIGHT behind it, but I'll give 'er a shot.

Just don't want to install a pitot tube on the hull only to find out it was th gauge that was busted.
 
The main tube is fine. Found the little disconnect and hooked up my little hand pump. It went right up to 30mph. Could still be partially clogged, but we'll see.

The problem is def. in the tube in my lower unit. I couldn't get air to blow through it enought to tell it was working. So again, I hooked up the little pump and this time used a tuperware container of water on the intake side. The outflow hose busted off due to all the pressure and sprayed water everywhere (mostly on me).

Looks like I found my problem.

Stuck drill bits in the hole and they all turned freely as far as my fingers could get them to go in. Does this just sound like a jam I can't reach or another problem?

Off to the store for some compressed air!
 
Did you check the intake hole on the leading edge of the gear case? Mine is epoxied closed in this image as I use an external p/u...

LU1.png
 
Yes, I checked what I believed to be the intake. It's on the driver's side, offset from th emiddle by about 2" and about 6-8" up from the bullet?

If so, I did.

No luck there. Bought some compressed air today (I miss having a compressor)
 
Sure enough, I was looking at the wrong hole. This one was TINY, but right where you said it would be. Stuck the drill bit in there and warm watter started to trickle out. Looks like so drift wood got stuck in there.

She should work tomorrow! Thanks for all the pointers.
 
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