Nasa target log impellor

[Dellquay13]

I've fitted a new impellor and spindle to the log unit because the magnet had corroded and stopped the impellor from spinning, and it now runs freely.
I've had the boat put back in today, and the log isn't reading speed or distance, although I could reset the trip counter ok, so i guess the head unit is fine.
are there any tests i can do on the transducer when underway, like metering the resistance to look for drops or spikes?
I'm really not forward to trying to fit a new transducer while afloat, I might have to look for a beach to dry out on while i do it.

 

[Poignard]

I've fitted a new impellor and spindle to the log unit because the magnet had corroded and stopped the impellor from spinning, and it now runs freely.
I've had the boat put back in today, and the log isn't reading speed or distance, although I could reset the trip counter ok, so i guess the head unit is fine.
are there any tests i can do on the transducer when underway, like metering the resistance to look for drops or spikes?
I'm really not forward to trying to fit a new transducer while afloat, I might have to look for a beach to dry out on while i do it.

Did you check that the impeller could spin freely with the log unit in place in its tube?

It may be something is stopping it spinning, eg a blob of antifoul or bit of weed.

Removing the impellor while afloat is no problem. There should be a blanking cap to screw on to the tube when you have extracted the log transducer, or you can just put the palm of your hand over it.

 

[Dellquay13]

Did you check that the impeller could spin freely with the log unit in place in its tube?

It may be something is stopping it spinning, eg a blob of antifoul or bit of weed.

Removing the impellor while afloat is no problem. There should be a blanking cap to screw on to the tube when you have extracted the log transducer, or you can just put the palm of your hand over it.

i checked it spinning freely with the new paddle wheel when i was antifouling. I switched it on as I left the boat yard pontoon and it just read 0.0kts, so weed shouldn't be a problem. I've no history of how it was before, the previous owner never moved the boat from their berth in the marina.

 

[penfold]

As Poignard says, getting it out to check and clean is straightforward; I don't think the NASA hull fitting has a flap but as long as you put the cap on quickly or cover with an available hand the amount of water that comes in won't fill a bucket. While it's out twirl the paddlewheel and see if it shows on the display.

 

[Dellquay13]

I've pulled the transducer out, twirled the wheel freely by hand, and it reads on the display.
I put it back in place, but I'm still not getting a reading when underway.
the boat has only been in the water for 15 days, and the log didn't work from launch day, so it isn't any kind of growth.
Does anyone have any suggestions before i have to go snorkelling in a very chilly Bristol channel to spin the wheel manually in situ?

 

[wallacebob]

Is it oriented the correct way? Mine has an arrow, others have a pointed arm.

 

[Rappey]

Never had any paddlewheel log last more than a few weeks before ceasing to work..
I do like the sound of this
Electromagnetic Log 2 (transducer and data box) - Nasa Marine Instruments

 

[Dellquay13]

Is it oriented the correct way? Mine has an arrow, others have a pointed arm.

yes i checked that

 

[Dellquay13]

Never had any paddlewheel log last more than a few weeks before ceasing to work..
I do like the sound of this
Electromagnetic Log 2 (transducer and data box) - Nasa Marine Instruments

it's a bit pricey at the moment, when there are other purchases on board more urgent than knowing my speed through water instead of my SOG from my plotter