View Full Version : 86' with Speedo issues
06-18-2011, 03:47 PM
We have an '86 Mastercraft with of course, dual speedos. One stopped working, now the other is getting flakey. I have tried the old tricks about cleaning out the pickups to no avail. I am thinking, because they are original and 25 years old, it might be time for some replacement parts.
From what I can tell, there are 4 "parts"... the pickups, the tubing, the speedo itself, and next to the gas tank, a vertical brass tube (although I have no idea what this is for).
Hoping I don't have to replace the actual gauges, any recommendations on what I SHOULD replace other than tubing?
Thanks ahead of time....
06-18-2011, 06:35 PM
you could remove speedometers and apply air pressure directly to gauge from a hand held vacuum, pressure pump, caution do not use a lot of pressure to check and see if the problem is the gauges or its somewhere from the gauges to the pitot tubes.
Tons of info on this site, including what the brass tubes are for:
Also, the most common point of failure is the pickups on the back of the boat. I bought two of these and have not had any issues since, just make sure your hose is in good condition as well:
These are a far superior design than the originals, and do not clog nearly as much.
+1 on being very careful about applying air pressure to the system, it doesn't take much to break those internal diaphrams.
06-19-2011, 12:40 AM
disconnect the tubing from the speedometer and blow air backwards through the system. You should be able to make the speedometer needle move with mouth pressure. You may need to replace the 25 year old tubing or pitots.
06-19-2011, 08:53 AM
You may want to look into adding a small compressor into your system. I bought my boat with one already installed and it works killer. It has air toggle switches that shut off the air to the speedos. Then you flip the switch for thr compressor and air flows out the the Pitot's and pushes out debris. I have used it twice this year and I don't have to get out of my seat to fix the clogged speedos. With all the water in CA this year there is a lot of debris. Let me know if you want to see some pics