speedo

[mikeruta]

I think my speedometer is reading slow. I have universal pitot tube on the back of the boat that looks clear and a small hose that runs to the speedo. I am going to check it beside another boat and I was wondering if the speedometer is adjustable? I have a 1991 17ft. Ebko Marine with a 3.0 Merc I/O Anybody know?

 

[gaugeguy]

Re: speedo

Some mechanical speedos have an adjustment screw on the back, and some that are under the glass and inaccessible. Others have a "horseshoe" inside that is used for adjustment, but again it is inaccessible. The problem with making adjustments on pitot speedos is that it is a total span adjustment. What that means is that if you increase the range at say 40 mph it throws off your 0, so you could be going 20 mph and your speedo will read 0.<br /><br />The pitot tube speedo is inherently inaccurate. Best bet if you want an exact speed reading is to go with a gps speedometer.

 

[Realgun]

Re: speedo

The Pitot tube speedo are more for show than anything. Some are very accurate due to being used in competition ski boats but most are off by 5-10 mph.

 

[gaugeguy]

Re: speedo

Originally posted by Realgun:<br /> The Pitot tube speedo are more for show than anything. Some are very accurate due to being used in competition ski boats but most are off by 5-10 mph.

Competition boats use a paddle wheel speedometer that has an adjustment potientiometer that they sync with a GPS and a device called "Perfect Pass". There are usually 2 of these PW speedos on a single boat.