In-dash speedometer troubleshooting

[32backnine]

I have a 1983 Johnson 150 that came with an in-dash speedometer which does not register at all, even at faster speeds. Anyone have suggestions to troubleshoot? The hose is free and clear from the lower unit fitting to the speedometer. The speedometer does work when low air is applied.

 

[tashasdaddy]

Re: In-dash speedometer troubleshooting

it is a low pressure system, the water applies pressure to the air in the tube, which registers on the speedo. check for air leaks in the line.

 

[psteurer]

Re: In-dash speedometer troubleshooting

A quick way to clear it is to remove the rubber tube from the back of the speedo and blow. You can use your mouth or if it is really clogged get something mechanical to blow. I presume you have a pitot attached to transom. Something could be clogged in there as well. You could also have a pinch in the rubber tube somewhere between the speedo and pitot.

 

[arnettjs]

Re: In-dash speedometer troubleshooting

As a new boater, I had the same problem. This may be of help....the pitot tube must be facing 'down' and not straight out (90 degree angle). Its fairly easy for the pitot to hit something and rotate up.

 

[32backnine]

Re: In-dash speedometer troubleshooting

The hose is free and clear with no leaks and when low air is applied, the speedometer does register. I guess to clarify, what do I look for to produce the air or pressure coming out of the lower unit of the engine. There is a plastic L-fitting on the motor which this hose is attached. I have no pitot attached to the outside of the transom. Remember the pressure on this type of speedo is produced from the lower unit. Hope this explains things better.

 

[bktheking]

Re: In-dash speedometer troubleshooting

The hose is free and clear with no leaks and when low air is applied, the speedometer does register. I guess to clarify, what do I look for to produce the air or pressure coming out of the lower unit of the engine. There is a plastic L-fitting on the motor which this hose is attached. I have no pitot attached to the outside of the transom. Remember the pressure on this type of speedo is produced from the lower unit. Hope this explains things better.

It's water pressure that is fed from that L fitting coming from the front of the lower unit. Run the boat in water until water comes out of the tube, sometimes an airlock can occur causing the speedo to stop working. Connect the tube and restest, I've had this happen with my speedo, seems to happen from sitting.

 

[R.Johnson]

Re: In-dash speedometer troubleshooting

Put a hose on the grearcase nipple. Should pass air. Or any air pasage has to be open. If you can't blow a reading from back , you have a leak, blockage, or faulty guage.

 

[bktheking]

Re: In-dash speedometer troubleshooting

Put a hose on the grearcase nipple. Should pass air. Or any air pasage has to be open. If you can't blow a reading from back , you have a leak, blockage, or faulty guage.

Doesn't water flow up to the gauge? Mine does.

 

[R.Johnson]

Re: In-dash speedometer troubleshooting

bktheking: Not if you can't blow air through it. And no! Air pressure move's the guage.

 

[bktheking]

Re: In-dash speedometer troubleshooting

bktheking: Not if you can't blow air through it. And no! Air pressure move's the guage.

Not on my 83 johnson it doesn't, pull that line off while under way and it will soak you.

 

[bktheking]

Re: In-dash speedometer troubleshooting

Not on my 83 johnson it doesn't, pull that line off while under way and it will soak you.

Actually we are both right, water travels up the tube and pushes air into the speedo, that's why when the tube is disconnected water should flow, no water should reach the speedo tube

 

[32backnine]

Re: In-dash speedometer troubleshooting

So I should probably pull the hose from the back of the speedo, get underway just to see if water is getting thru, then remove some of the water out of the speedo end of the hose to create an air pressure void. Reconnect the hose, get underway to hopefully have the speedo working. It will register as is blowing from the motor end of the hose. If you think I have it correct I want to THANK ALL for the info you have given me.

 

[tashasdaddy]

Re: In-dash speedometer troubleshooting

there is not suppose to be any water in the tube!!! when the running water will enter the pickup, and tube pressurizing the air in the tube, thus activating the speedo. water in the speedo itself will ruin it quickly.

 

[psteurer]

Re: In-dash speedometer troubleshooting

If you can get the speedo to register by blowing air into end of the tube not connected to the speedo, then you have an obstruction in pick-up in the motor. You need to blow it out or clean it out. And I will add that if you dock your boat for periods of time with the motor down you will continue to get these type of clogs.

 

[Silvertip]

Re: In-dash speedometer troubleshooting

Clean the pitot on the engine. It is clogged with debris. Or blow backwards though it at the fitting, not through the tube. This is an entirely closed system. Water cannot flow though it. If water flowed into the speedo it would have to have an exit meaning there would need to be another line dumping water overboard. Ever tried to blow into a soda bottle? Water pressure at the pitot compresses air in the line. That compressed air unwinds a Bourdon tube in the speedo that causes the needle to move. If the Bourdon tube gets water in it and you happen to live in an area where it freezes, every speedo in that area would be junk every spring. Obviously water will come out the tube if you pull it off the back of the speedo when under way because it is no longer a closed system.

 

[32backnine]

Re: In-dash speedometer troubleshooting

I went to my garage and pulled the hose off at the L-fitting. I tried to blow (by mouth) thru the tube to see if I could get a read at the speedo. I get no read using physical air pressure. I then used compressed air holding the compressor hose end slightly away from the hose end. Speedo worked fine. Any suggestions to clear from the L-fitting back into the lower unit. What do I look or listen for to be sure the origin of the air pressure is doing what it is supposed to?

 

[Cricket Too]

Re: In-dash speedometer troubleshooting

Do water pressure gauges have water flow all the way to the gauge? I always thought they did, but now that Silvertip mentions it, it seems like there would need to be another line dumping the water somwhere.

Is it the same principle with water pressure gauges, the water from the engine compresses the air in the tube and gives you a water pressure reading?


32backnine....Take a look on the bottom of the pitot (L-fitting) and there should be a little metal ball type looking thing, clean that whole area off, and then take your compressed air and blow backwards from where you take the hose off, so that you are blowing back out if the botom of the pitot (L-fitting).

 

[32backnine]

Re: In-dash speedometer troubleshooting

I'll look at that. Kinda hard to get in a position to see in there. Maybe I need to purchase another L-fitting if it operates like a ball valve. Unsure what is inside that fitting if anything. I know that part can be purchased. Is there anyway to blow air pressure out of the engine thru that L-fitting?

 

[tashasdaddy]

Re: In-dash speedometer troubleshooting

just connect a small hose to the L fitting and blow it out. if it will not clear, just add a pitot to the transom and connect it.

http://www.iboats.com/Boat_Parts_Ac...62207--submit.Search--submit.x.42--submit.y.4

 

[bktheking]

Re: In-dash speedometer troubleshooting

I'll look at that. Kinda hard to get in a position to see in there. Maybe I need to purchase another L-fitting if it operates like a ball valve. Unsure what is inside that fitting if anything. I know that part can be purchased. Is there anyway to blow air pressure out of the engine thru that L-fitting?

There is no valve in the l fitting, I replaced mine 2 years ago, it's just straight through.