Old as Dirt!
Join Date: Nov 2008
Location: Tampa Bay Area
Thanked 130 Times in 123 Posts
Rep Power: 7
Re: Speed Log out by around 3 knots
"when the display shows 2 knots my handheld GPS will show 5"
In other words, your waterwheel is VERY SLOW.
When is the last time you removed the impeller and cleaned it out? Sometimes you'll find enough growth in there to freeze it up in just a week or two. I'll pull the log whenever the boat is being left at the mooring, and if it has been left in, it gets cleaned (old toothbrush) picked (dental picks) and if there is barnacle crud on it, you may need to soak it in vinegar as well.
Before you decide something needs calibrating--pull it and see if it isn't just crud.
Tho' it may sound odd, I have found that applying Neosporin anti-bacterial ointment to the paddle-wheel and inner faces of the transducer housing significantly extends periods between cleanings.
"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."