i50 Tridata erratic speed readings

[jumby]

i50 Tridata with depth, speed (ST800-P120) and wind transducers connected installed below deck at nav station. Individual wind, depth, speed displays networked and set as repeaters in cockpit. Depth and wind functioning properly. Repeaters functioning properly.

Speed readings are erratic. Motoring at 4-5 knots the speed reading will jump to 8 knots then back to 4, then jump to 14 knots then back to 4. At times, sitting dockside it has read 1-1.5 knots with no current present at slack tide.

Done to date: At suggestion of Raymarine tech support have done multiple speed calibration runs over a measured nautical mile to no avail. Also as suggested by support checked the transducer paddle wheel with a compass to ensure correct polarity of magnets. Have done a dockside calibration for speed offset. Have replaced display. Have replaced transducer. All to no avail as the unit still has erratic readings.

This is installed on a very basic Island Packet 32. The only 110v systems on the boat are a water heater, battery charger and outlets. While motoring no 110v is present. While motoring the only current present is the alternator charging batteries. When reading speed at dockside there is no shore power present, no charging going on. The wiring and transducer runs are following the previous installation of instruments (autohelm) that were in use for at least 15 ish years with no such problems. When replacing the transducer I even installed it into the thru hull fitting and ran the transducer wire directly to the tridata from the bilge, through the cabin bypassing any and all existing wire runs with no difference. I ran it to the speed display in the cockpit and made it the master with no difference.

At this point I have no idea what to check or do to resolve this. From raymarine what I am getting is send everything back to them for service. I have a hard time believing two sets of displays and transducers are at fault. I'm not past thinking I have somehow missed something that is causing this but feel fairly certain the integrity of the install is pretty good.

Little help?

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Jumby,

The instrument repair technician has recommended changing the speed response from 9 to 4 or to 3 to address the reported symptom.

[jumby]

Thank you. In talking to support previously they said to turn it down to 10 if my memory serves. I'll drop it to 4 or 3 and give it a sea trial.

[jumby]

No joy. Took boat out for a seatrial. Response rate at previous setting of 10 and it was all over. 4 knots, 11 knots, 6 knots. Turned response down to 3 and it was no better. Turned it down to 1 and it was as close at it has ever been but from a true boat speed of about 4.8 to 5 it would jump as high as 8.

Any more suggestions???

[Chuck - Raymarine - Moderator]

Jumby,

It is recommended that the i50 Tridata be tested again after having disconnected it from the network. Depending upon how the system has been installed, it may be necessary to either
- temporarily disconnect all other devices from the SeaTalkng backbone / SeaTalk bus or
- disconnect the i50 Tridata from the SeaTalkng backbone and power it using the SeaTalkng Power Cable packed with the i50 Tridata.

[jumby]

Will do. Thank you!

[Chuck - Raymarine - Moderator]

You're welcome.

[jumby]

Well. Did as you suggested. The bus at the nav station has power, the tridata, an i60 wind and the network cable going to the cockpit instruments. Disconnected the i60 wind and network cable going to the bus in the cockpit. That left only the tridata with speed and depth transducers being powered. This produced no change in the speed readings being erratic. Then disconnected the depth transducer and the speed started working. It read correctly with no erratic fluctuations. Ran the boat for about half an hour with no change. Powered the system down and reconnected the depth transducer to the tridata. It still worked correctly. Reconnected the cockpit instruments to the bus and it still worked correctly.

So at the moment it is working as it should and it appears that disconnecting and reconnecting the depth transducer fixed the issue. Which makes absolutely no sense to me but if it works...

I'm going to seatrial it again in another day or so and fingers crossed will continue to work correctly.

[Chuck - Raymarine - Moderator]

jumby,

I'm a bit confused the cause / effect symptom, but glad to learn that the problem appears to have been resolved. Should the problem re-occur, then please respond accordingly.