speedometer or pitot question

dlogvine

Master Chief Petty Officer
Joined
May 4, 2015
Messages
832
When Ive got my boat, speedometer was not working at all, so I found the same speedometer on the salvage yard and replaced the old one. Replaced speedometer showed up the speed of 10-15mph max even when I was going at about 30-35mph. Id guess that this time the problem is with the pitot or the tubing. Is there any way to check the speedometer components before replacing them?
 

dozerII

Admiral
Joined
Oct 25, 2009
Messages
6,527
Take the tube off on both the speedo and pitot ends and blow through with compressed air to check for blockage. Put a short piece of tube on the pitot tube and try to blow through it with your mouth it may be partially blocked by sand or what have you.Connect the main tube to the speedo and use your mouth to blow into the other ens and have someone watch the gauge you should see some movement , may 5 mph.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Before you do anything else, be certain the pitot tube is clicked in position ALL the way down. Sometimes the tube will be pushed up slightly by trailer bunks or by hitting an object in the water. It will then read low. If it kicks up all the way it will not read at all.
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
If you have real doubts as to the pitot tube, just buy another one and replace it. They are really cheap and basically made the same from one to another. Also make certain the tube going from the gauge to the pitot pick up is clear with no obstructions in it anywhere. Such a speedometer is merely a pressure gauge calibrated in MPH corresponding to the pressure in the tube from the water...
 

dlogvine

Master Chief Petty Officer
Joined
May 4, 2015
Messages
832
I installed new tube and pitot will see if it will fix the problem
 

64osby

Admiral
Joined
Jul 28, 2009
Messages
6,799
Hope it did fix it. IMO they are a guideline for speed at best. If you really need to know use a gps app on your phone.

A more important gauge for your boat is a tach. It lets you know if your motor is running at spec, not over revving or bogging down.
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
On mine the little hole with sometimes get junk in it when running in shallow water with weeds. It will usually clean itself out but yours might be different.
 
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