Only 1 of 2 speedo's working

[wake beater]

Last year both my speedo's worked perfectly,this year only the left one register's mph's.What could it be.My boat is a 21 ft Mariah ,1991.

[mapleleaf]

If they're the old vacuum line style, can't remember the proper name, the line for the right speedo is broken somewhere...
If there's a grey 1/4" tube coming from the pitot on the transom, you've got the air speedo and it's busted somewhere,
The pitot;s can get broken pretty easily when they're almost 20 yrs. old, I'm notsure if there's a possible fix, I think it's upgrade and replacement time...
I'm having the same problem with my leftside speedo reading irradically, it's just further down my repair list!!!!
I would check all the fitting's first, one on the transom, one under the dash and if you can see the inside of the transom I think there's a connection behind where the pitot is on the outside of the transom, those vacuum lines are a part of the wiring chase that go from the dash to the gas tank and transom light.....

[saltare inverts]

Usely when I have that problem there is blockage at the entry point. I keep a small drill bit on boat and clean it out in the water. If that doesnt do it blow it out from back of speedo toward rear of boat with air compressor.

[csuggs]

Same as Saltare. One reason that there are two speedos is because clogged pitot tubes are common - hopefully leaving one speedo working at all times. I keep a wire (from a utility marking flag like you get at Lowe's or Home Depot) in the truck and everytime I pull the boat out I run that wire through the pitot. I have the "flow-thru" tournament pitots that allow the wire to pass all the way through. FYI - most days out I get debris in at least one pitot. Sometimes I can clear it in the water just be reversing the throttle between sets.

[DKJBama92Mariah]

Yup. Just clean the little hole in the pitot with a piece of wire. Happens all the time. I had to replace one of my pitot assemblies as it was removed by a log. The one I replaced it with from skidim has a bigger hold and does not seem to clog as easily.

[Montgomery]

My left side speedometer on my 91 Sunsport stops working every once in a while and usually I have to reach up under the dash and tighten the hose/line thing that attaches to the back of it and then it works just fine but lately the cause has been the actual speed sensor thing on the left side that hangs off the bottom of the boat it hinges up and the water doesn't hit it right so it doesn't read right but I just reach under the platform and push it back down and it works just fine again. Those are the only problems I've had with mine

[wake beater]

Today I tightened the hose on the back of the speedo,still didn't work.Is that what I am supposed the clean with a piece of wire? Those little up side down fins with a cable attached to them is what I should wiggle ,attached to back corners of hull?

[csuggs]

Wake Beater - In the attached picture, look at the pitot tube which is circled in red. That's what you need to keep clean. Mine being a "flow through" type tube, I am able to run a wire through the hole in it (from front to back) to keep it clear of small debris that clogs it up, keeping the speed from working. Yours may not be the same, depending on the style of pitot that you have. The original one's are not a flow through style, but need to be kept clean none-the-less. After you make sure that all of your 1/4" tubing fittings are tight with no leaks (all the way from the pitot to the back of the gauge), then all you should have to do is keep the pitot inlets clean. ;)

Another place to check is harder to get to, but if you have your seat removed, you can access the two bronze tubes that the speedo tubing goes into. One of mine was cracked and split from where moisture had intered and frozen. (You can see the swolen ends on the one on the left in the picture). The bronze tubes are supposed to dampen or stabilize the pressure in the tubing so the speedo needle doesn't "jump" on the gauge.

[wake beater]

Thanks alot csuggs,cleaned mine with a peice of tie wire and then shot some air at it,.Yesterday we were on the lake and the other speedo went out. There was alot of leave's and needle's(in this strip) drove through ,other speedo failed.Stopped after I got past this 50 ft strip,then went again speedo worked .Hopefully the other is fixed..

[csuggs]

Good - glad to help. Just be careful with compressed air - you could blow a line off somewhere between the pitot and the speedo, or you might even damage the gauge. I think once you get them working again you'll be able to keep them clean with the wire.:D

[wake beater]

Ok ,I didn't put the compresser air to it.Went out again yesterday and it still was not working ,but the left one still works fine.Tried cleaning with wire but there are little metal caps on back of pitot.

[ngavchris]

Take the hose off the pickuptube and try blowing air backwards. Do not blow air up the hose. It will definitely tear up your speedometer. This I say from past experience.