my log has either broken suspect paddle wheel caesed are different manufacturers interchangeable with skin fitting

Hi Steve, if your log stops working, nine times out of ten it will be the paddle wheel. Have you tried taking it out and giving it a good scrub? (You should have a blanking plug to enable you to do this. A frightening-looking amount of water will come in as you pull out the transducer, but as long as you are quick with the plug it will only be about a teacup full!)
Alternatively the paddlewheel may be worn or the pin it spins on bent. Replacing either or both may provide a cure.
Unfortunately the parts are not interchangeable between different manufacturers. What make/model is your log? There are companies who specialise in keeping parts of out-of-date electronics, so the chances are that you will be able to get a replacement, even if it is a few years old.

Be brave and quick when you pull the plug and make sure you have a blanking plug-and just in case a suitable something to push down the hole-the sealing flaps do work but can leak sometimes!
Phil

Mick Pindar
Have paddle wheel log for many years and they fouled up on a regular basis with shrimps, crabs and the odd bit of seaweed living in the housing to barnacles taking up dwelling on the paddle wheel. My paddle wheel and housing was in a small locker which I had glassed in to make waterproof so the water that came in was restrained to a small area which was very easy to bail out and dry. A small retaining box round the housing would do the same trick. I never understood why the manufacturers never mouldede the paddle wheel etc. in a copper loaded plastic which might reduce the fouling. Mine was a NASA log.
Mick Pindar

Well after my earlier mail-I completely forgot to check mine before going off earlier this week!-after some 80mls.it began to show half a knot-cleaned it but whilst under influence of a hangover and forgot to align it along the hull!-so only got about two knots out of it for next 30 mls!!

after previous enquiry i felt ihad not explained the problem re paddle wheel of my silva log. ive checked and cleaned the paddle wheel again but my unit shows a garbled screen. so im at a loss whether it is the paddle wheel or if the unit needs changing.

What do you mean by "garbled". Is it telling lies, or is it simply illegible? The problem with today's wonderful electronics (or maybe it is why they are wonderful) is that being solid state and waterproof they are almost impossible to repair. We recently returned our ST 60 wind instrument to Raymarine. They told us it needed a new PCB (primary circuit board?) and it would cost almost as much to repair as it would to part exchange it for a new one. And the new one would come with a two-year guarantee as against six months for the repair. So it was no contest.
The only saving grace is that marine electronics continue to fall is price, relative to most things, anyway.
How old is your log? Is the model still available?

hi cathy yes the on going saga re my silva log garbled screen showing 888 plus other unraedable print guess ive just got to bite the bullet once again 1 silva log required thanks to all for input nice to know your all there Steve Smith

Don't throw it away, it sounds as if the LCD screen has got damp in it.
There's a simple trick to this.
Open up access to the rear of the unit, you probably will not have to take the back off, most have a breather tube.
Gently play a hair dryer all over the unit for 5-10 minutes and hey-presto it will be restored to as new functionality.
By the way, if anyone is worried about letting water in the boat when taking out a log impellor, get a bin bag, tie a bit of light cord (string) on each corner then slide down over the hull so it is positioned roughly over the fitting, then when the hull is opened, the inrush of water sucks the bag over the hull and seals it perfectly. This also works for servicing skin fittings - I have stripped down Blakes (rather leaky) skin fittings many times using this technique.
Its just a modern version of how they plugged cannon ball holes in Nelson's day.
Many years ago I had a racing dinghy holed, we deliberately sailed over the spinnaker and the inrush of water stopped - a useful tip to remember if you are ever holed at sea!

will try drying out unit many thanks for tip david