Navman fish finder for speedometer

Ribnot · 30 March 2004, 15:59

I was advised to get a fishfinder to give me speed, depth, water temperature and, of course, find fish instead of buying seperate instruments to save money. I had it fitted by a marine engineer but when i exceed about 10 knots the screen goes fuzzy and is quite useless. I can check speed on the Garmin 176c GPS (not bought in US, they do have a different base map) but it will not give me real speed over water, just over land. Can someone let me know what might be wrong.

Jizm · 30 March 2004, 18:40

I had the same problem using a nanvman 440.
Get someone else to drive the boat and look over the transom to check that the transducer is in undisturbed water flow not turbulent with air etc, or it will not work when under way.
Easiest thing to do is remove the transduducer and carefully hold it in several different places (screw it to a piece of scrap timber)until it works porperly. Saves drilling lots of holes in the transom.
regards
Jiz

Ribnot · 30 March 2004, 20:12

Thanks. I was thinking that they might all be the same at speed but it sound about right that it was fitted wrong. Nothing new with this boat.